Lightguide comprising a low refractive index region

ABSTRACT

In one embodiment of this invention, a lightguide comprises a low refractive index region disposed between light extracting region and a non-scattering region. In further embodiment of this invention, volumetric scattering lightguide comprises a low refractive index region disposed between a volumetric scattering region and a non-scattering region. In some embodiments, a light emitting device comprising a volumetric scattering lightguide can angularly filter light input into the edge of a volumetric scattering lightguide by controlling the refractive index of the low refractive index region relative to the refractive index of the non-scattering region to prevent direct illumination of the volumetric scattering region, provide a luminance uniformity greater than 70%, or improve the angular luminous intensity of the light emitting device. The volumetric scattering lightguide may be curved, tapered, and a light emitting device comprising the same may further comprise at least one light source and a light redirecting element.

RELATED APPLICATIONS

This application is a continuation-in-part application of U.S. patentapplication Ser. No. 11/848,759, filed Aug. 31, 2007, now abandoned, andis a continuation of U.S. application Ser. No. 11/223,660, filed Sep. 9,2005, now U.S. Pat. No. 7,278,775, which claims benefit of provisionalapplication Ser. No. 60/608,233, filed Sep. 9, 2004, the disclosures ofeach are incorporated by reference in their entirety herein.

FIELD OF THE INVENTION

This invention generally relates to optical components and lightemitting devices comprising optical components for illumination andmethods of manufacturing the devices and components.

BACKGROUND OF THE INVENTION

Edge-illuminated lightguides have been used in backlights for LCDs andmore recently for light fixtures. For extended color, longer lifetime,increased optical efficiency, and cost, LEDs are becoming utilized morein backlight assemblies instead of CCFLs. Since LEDs are closer to beinga point source, LED light can be controlled more efficiently than theextended source CCFL. However, by using the same white spot diffusersnoted above in light guides, the light is scattered in all directions,up to the critical angle of the light guide air interface. The refractedangular spread of light out of the light guide can reach anglesapproaching 90 degrees from the surface. Additional diffuser films usedto reduce the visibility of the white dots spread this light furtherinto undesired, i.e., wider, angles. Optical films such as prismaticfilms are then necessary, to “rein in” a portion of this light backtoward 0 degrees (the direction perpendicular to the surface). Thus,between the white dots spreading light out into larger angles thanneeded, and then using collimating films to bring a portion of thislight back toward the normal or desired viewing angles, a significantamount of light is lost and the process is an inefficient one.

Other backlight configurations have been proposed using symmetricscattering particles instead of white dots. Scattering light guides havebeen described as “highly scattering optical transmission” (HSOT)polymers by Okumura et al (J. Opt. A: Pure Appl. Opt. 5 (2003)S269-S275). The authors demonstrated that a backlight based upon a HSOTpolymer has the potential to provide twice the brightness of aconventional backlight. However, the particles used are symmetric orspherical in shape. The Okumura teachings do not account for theasymmetric nature of the input light, or the need for more light to bediffused vertically, horizontally, or out from the main face of thelight guide. Also, traditional designs using planar lightguides such asused with LCDs have angular output, thermal, uniformity, efficiency, andform factor limitations. Light from light sources such as LEDs that areincident upon a volumetrically scattering lightguide can havesignificantly bright regions near the LEDs due to light directlyreaching the volumetric scattering region and causing bright luminancenon-uniformities on the light emitting surface near the edge of thelightguide. If the diffusion strength (angular FWHM intensity of thediffusion profile) of the volumetric light scattering lightguide issignificantly reduced to try and prevent the high luminancenon-uniformity near the edge, the optical efficiency of the lightguideis also reduced.

SUMMARY OF THE INVENTION

In one embodiment of this invention, a lightguide comprises a lowrefractive index region disposed between light extracting region and anon-scattering region. In further embodiment of this invention,volumetric scattering lightguide comprises a low refractive index regiondisposed between a volumetric scattering region and a non-scatteringregion. In some embodiments, a light emitting device comprising avolumetric scattering lightguide can angularly filter light input intothe edge of a volumetric scattering lightguide by controlling therefractive index of the low refractive index region relative to therefractive index of the non-scattering region to prevent directillumination of the volumetric scattering region, provide a luminanceuniformity greater than 70%, or improve the angular luminous intensityof the light emitting device.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional side view of a traditional liquidcrystal display backlight;

FIG. 2 is a schematic cross-sectional side view of one embodiment of anenhanced LCD backlight of the invention utilizing CCFL light sourceswith asymmetric particles contained within the light guide;

FIG. 3 is a perspective view of the embodiment of FIG. 2;

FIG. 4 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention utilizing LEDs with asymmetric particlescontained within the light guide;

FIG. 5 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention utilizing LEDs with asymmetric particles ofvarying densities contained within the light guide;

FIG. 6 is an example of a side emitting LED from LUMILEDS Inc.;

FIG. 7 is a perspective view of an LCD backlight utilizing side-emittingLEDs (Prior Art);

FIG. 8 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention utilizing side-emitting LEDs with asymmetricparticles contained in a region optically coupled to the light guide;

FIG. 9 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention utilizing two CCFLs with asymmetric particlescontained in a region optically coupled to the light guide;

FIG. 10 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention utilizing two CCFLs with asymmetric particlesof varying densities contained in a region optically coupled to thelight guide;

FIG. 11 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention utilizing two CCFLs with two regionscontaining asymmetric particles aligned with their axis crossed andoptically coupled to the bottom of the light guide;

FIG. 12 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention utilizing two CCFLs with two regionscontaining asymmetric particles aligned with their axis crossed andoptically coupled to the top of the light guide;

FIG. 13 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention utilizing two CCFLs with two regionscontaining asymmetric particles aligned with their axis crossed andoptically coupled to the top and bottom of the light guide;

FIG. 14 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention with asymmetric particles contained withinthe tapered light guide and two CCFL light sources;

FIG. 15 is a perspective view of one embodiment of an enhanced LCDbacklight of the invention utilizing two CCFLs with a light guide regioncomposed of two regions containing asymmetric particles aligned withtheir axis crossed;

FIG. 16 is a perspective view of one embodiment of an enhanced LCD ofthe invention using the enhanced backlight of FIG. 9;

FIG. 17 is a perspective view of one embodiment of an enhanced LCD ofthe invention using the enhanced backlight of FIG. 9 and two crossedcollimating films;

FIG. 18 is a perspective view of one embodiment of an enhanced LCD ofthe invention using the enhanced backlight of FIG. 9 and two crossedcollimating films and an additional diffuser;

FIG. 19 is a perspective view of one embodiment of an enhanced LCD ofthe invention using the enhanced backlight of FIG. 9, two crossedcollimating films and a reflective polarizer;

FIG. 20 is a perspective view of one embodiment of an enhanced LCD ofthe invention using the enhanced backlight of FIG. 9, two crossedcollimating films with one of the collimating films containingasymmetric particles;

FIG. 21 is a perspective view of one embodiment of an enhanced LCD ofthe invention using an enhanced backlight with a high refractive indexlight guide and a low refractive index coating with crossed collimatingfilms;

FIG. 22 is a perspective view of one embodiment of an enhanced backlightof the invention with a light guide positioned above cold cathodefluorescent lamps with varying concentration of dispersed phaseparticles;

FIG. 23 is a perspective view of one embodiment of a light guide used inthe enhanced backlight of FIG. 9;

FIG. 24 is a perspective view of one embodiment of a light guide of theinvention used with non-spherical particles in between the input andoutput surfaces of the light guide; and

FIG. 25 is a perspective view of one embodiment of a light guide used inthe enhanced backlight of FIG. 22.

FIG. 26 is a cross-sectional side view of a light emitting devicecomprising a volumetric scattering lightguide with a low refractiveindex region.

FIG. 27 is a cross-sectional side view of the light emitting device ofFIG. 1 illustrating component dimensions.

FIG. 28 is a cross-sectional side view of a light emitting devicecomprising a volumetric scattering lightguide with a spatially varyinglow refractive index region.

FIG. 29 is a top view of the light emitting device of FIG. 3 comprisinga volumetric scattering lightguide with a spatially varying lowrefractive index region.

FIG. 30 is a cross-sectional side view of a light emitting devicecomprising a light reflecting region on the same side of the lightguideas a volumetric scattering region.

FIG. 31 is a cross-sectional side view of a light emitting devicecomprising a light reflecting region on the opposite side of thelightguide as a volumetric scattering region.

FIG. 32 is a cross-sectional side view of a light emitting devicecomprising a curved volumetric scattering lightguide.

FIG. 33 is a cross-sectional side view of a light emitting devicecomprising a volumetric scattering lightguide with a low refractiveindex region and a specularly reflecting optical element.

FIG. 34 is a perspective view of a light emitting device comprising avolumetric scattering lightguide with a low refractive index region andasymmetric dispersed phased domains.

FIG. 35 is a perspective view of a light emitting device comprising avolumetric scattering lightguide between a low refractive index regionand a second non-scattering region.

FIG. 36 is a cross-sectional side view of a light emitting devicecomprising a volumetric scattering lightguide with a low refractiveindex region and surface relief light extracting features.

FIG. 37 is a cross-sectional side view of a light emitting devicecomprising a volumetric scattering lightguide with a low refractiveindex region varying spatially between the volumetric light scatteringregion and the non-scattering region.

FIG. 38 is a top view of the light emitting device of FIG. 37illustrating the regions where the volumetric light scattering region isdirectly coupled optically to the non-scattering region.

FIG. 39 is a cross-sectional side view of a light emitting devicecomprising a volumetric scattering lightguide with a low refractiveindex region varying spatially and an air gap region varying spatiallybetween the volumetric light scattering region and the non-scatteringregion.

FIG. 40 is a top view of the light emitting device of FIG. 39illustrating the pattern regions where the volumetric light scatteringregion is directly coupled optically to the non-scattering region andwhere there is an air gap region between the volumetric light scatteringregion and the non-scattering region.

FIG. 41 is a cross-sectional side view of a light emitting devicecomprising a volumetric scattering lightguide wherein light at an anglelarger than the critical angle for the interface between thenon-scattering region and the low refractive index region totallyinternally reflects.

FIG. 42 is a cross-sectional side view of a light emitting devicecomprising a curved, tapered volumetric scattering lightguide and alight redirecting element.

DETAILED DESCRIPTION OF THE INVENTION

The features and other details of the invention will now be moreparticularly described with reference to the accompanying drawings, inwhich embodiments of the inventive subject matter are shown. It will beunderstood that particular embodiments described herein are shown by wayof illustration and not as limitations of the invention. However, thisinventive subject matter should not be construed as limited to theembodiments set forth herein. Rather, these embodiments are provided sothat this disclosure will be thorough and complete, and will fullyconvey the scope of the inventive subject matter to those skilled in theart. The principal features of this invention can be employed in variousembodiments without departing from the scope of the invention. All partsand percentages are by weight unless otherwise specified. All patentapplications and patents referenced herein are incorporated byreference.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the inventivesubject matter. Like numbers refer to like elements throughout. As usedherein the term “and/or” includes any and all combinations of one ormore of the associated listed items. Also, as used herein, the singularforms “a”, “an” and “the” are intended to include the plural forms aswell, unless the context clearly indicates otherwise. It will be furtherunderstood that the terms “comprises” and/or “comprising,” when used inthis specification, specify the presence of stated features, integers,steps, operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

DEFINITIONS

For convenience, certain terms used in the specification and examplesare collected here.

“Speckle”, often referred to also as scintillation, includes the opticalinterference pattern visible on a scattering element or perceived ascoming from or near a scattering element. This can include color orintensity variations within an small area of interest.

“Speckle Contrast” is defined herein to include the ratio of thestandard deviation of the intensity fluctuation to the mean intensityover the area of interest.

“Scatter,” “Scattering,” “Diffuse” and “Diffusing” as defined hereinincludes light scattering by reflection, refraction or diffraction fromparticles, surfaces, or layers.

“Optically coupled” is defined herein as including the coupling,attaching or adhering two or more regions or layers such that theintensity of light passing from one region to the other is notsubstantially reduced due to Fresnel interfacial reflection losses dueto differences in refractive indices between the regions. Opticalcoupling methods include joining two regions having similar refractiveindices, or by using an optical adhesive with a refractive indexsubstantially near or in-between at least one of the regions or layerssuch as Optically Clear Adhesive 8161 from 3M (with a refractive indexat 633 nm of 1.474). Examples of optically coupling include laminationusing an index-matched optical adhesive such as a pressure sensitiveadhesive; lamination using a UV curable transparent adhesive; coating aregion or layer onto another region or layer; extruding a region orlayer onto another region or layer; or hot lamination using appliedpressure to join two or more layers or regions that have substantiallyclose refractive indices. A “substantially close” refractive indexdifference is about 0.5, 0.4, 0.3 or less, e.g., 0.2 or 0.1. Directly“optically coupling” a first and second region or material refers to theoptical coupling of the regions or materials wherein light travellingthrough the first region can directly pass into the second regionwithout passing through an intermediate region.

“Diffusion angle” is a measurement of the angular diffusion profile ofthe intensity of light within a plane of emitted light. Typically thediffusion angle is defined according to an angularFull-Width-at-Half-Maximum (FWHM) intensity defined by the total angularwidth at 50% of the maximum intensity of the angular light outputprofile. For light scattering regions, diffusive films and sheets, thisis typically measured with collimated light at a specific wavelength orwhite light incident normal to the film. Typically, for anisotropicdiffusers, the FWHM values are specified in two orthogonal planes suchas the horizontal and vertical planes orthogonal to the plane of thefilm. For example, if angles of +35° and −35° were measured to haveone-half of the maximum intensity in the horizontal direction, the FWHMdiffusion angle in the horizontal direction for the diffuser would be70°. Similarly, the full-width at one-third maximum and full-width atone-tenth maximum can be measured from the angles at which the intensityis one-third and one-tenth of the maximum light intensity respectively.

The “asymmetry ratio” is the FWHM diffusion angle in a first lightexiting plane divided by the FWHM diffusion angle in a second lightexiting plane orthogonal to the first, and thus is a measure of thedegree of asymmetry between the intensity profile in two orthogonalplanes of light exiting the diffuser.

A “spheroidal” or “symmetric” particle includes those substantiallyresembling a sphere. A spheroidal particle may contain surfaceincongruities and irregularities but has a generally circularcross-section in substantially all directions. A spheroid is a type ofellipsoid wherein two of the 3 axes are equal. An “asymmetric” particleis referred to here as an “ellipsoidal” particle wherein each of thethree axis can be a different length. Ellipsoidal particles can range inshapes from squashed or stretched spheres to very long filament likeshapes.

A “spherical” or “symmetric” disperse phase domain includes gaseousvoids, micro-bodies, or particles that substantially resemble a sphere.A spherical domain may contain surface incongruities and irregularitiesbut has a generally circular cross-section in substantially alldirections. A “spheroid” is a type of ellipsoid wherein two of the threeaxes are equal. An “asymmetric” domain is referred to here as an“ellipsoidal” domain wherein each of the three axis can be a differentlength. Typically, ellipsoidal domains resemble squashed or stretchedspheres. “Non-spherical” domains include ellipsoidal domains and otherdomains defined by shapes that do not resemble a sphere such as thosethat not have constant radii. For example, a non-spherical particle mayhave finger-like extensions within one plane (amoeba-like) andsubstantially planar in a perpendicular plane. Also, fibrous domains arealso non-spherical disperse phase domains that may have aspect ratios of10:1, 100:1 or larger.

“Light guide” or “waveguide” refers to a region bounded by the conditionthat light rays traveling at an angle that is larger than the criticalangle will reflect and remain within the region. In a light guide, thelight will reflect or TIR (totally internally reflect) if it the angle(a) from the surface normal does not satisfy the condition

$a < {\sin^{- 1}\left( \frac{n_{2}}{n_{1}} \right)}$where n₁ is the refractive index of the medium inside the light guideand n₂ is the refractive index of the medium outside the light guide.Typically, n₂ is air with a refractive index of n≈1, however, high andlow refractive index materials can be used to achieve light guideregions. The light guide may comprise reflective components such asreflective films, aluminized coatings, surface relief features, andother components that can re-direct or reflect light. The light guidemay also contain non-scattering regions such as substrates. Light can beincident on a light guide region from the sides or below and surfacerelief features or light scattering domains, phases or elements withinthe region can direct light into larger angles such that it totallyinternally reflects into smaller angles such that the light escapes thelight guide. Light may enter from any face (or interfacial refractiveindex boundary) of the lightguide region and may totally internallyreflect from the same or another refractive index interfacial boundary.A region can be functional as a lightguide for purposes illustratedherein as long as the thickness is larger than the wavelength of lightof interest. For example, a light guide may be a 5 micron region with 2micron×3 micron ellipsoidal dispersed particles or it may be a 3millimeter diffuser plate with 2.5 micron×70 micron dispersed phaseparticles.

“Planarized,” “Planarization,” and “Planar,” includes creating asubstantially flat surface on an element. A flat surface refers to onethat does not have a substantially varying surface normal angle across asurface of the element. More than one surface may be planarized. Astypically used herein, a material region is combined with a surface ofan element that has a surface structure such that the surface of thematerial opposite the element is substantially planar. Typically,planarized films or components can be easily laminated to anotherelement using pressure sensitive adhesives or hot-lamination withouttrapping air bubbles of sufficient size to affect the opticalperformance of the combined element. Coatings, such as thin coatingsused in some anti-reflection coatings can be applied more uniformly toplanarized elements.

“Arcuate” includes curves or surfaces wherein the surface normal changesangle as one moves along the surface. These can include continuouslychanging surfaces or curves as well as discretely changing (sharpcorners) transitions. The curves may be in more than one plane and maybe changing at varying rates in more than one plane. For purposes ofthis invention, the term arcuate refers to the “macro” changes or thechanges in the surface normal angles on the scale along the surface ofmeters, centimeters, or millimeters. The changes may be regular, random,repeated, semi-random, predetermined spacing or variable withconstraining conditions.

“Tapered” refers to the dimensional length, width, height, radius orother dimension decreasing along at least one direction. The dimensionmay decrease discretely, continuously, regularly, irregularly, randomly,etc. The dimension in two or more directions may decrease along one ofthe first two or a third direction. The dimensional length does not needto converge to a point in a give plane or direction. The taper may beover a particular region or portion of an element.

When an element such as a layer, region or substrate is referred toherein as being “on” or extending “onto” another element, it can bedirectly on or extend directly onto the other element or interveningelements may also be present. In contrast, when an element is referredto herein as being “directly on” or extending “directly onto” anotherelement, there are no intervening elements present. Also, when anelement is referred to herein as being “connected” or “coupled” toanother element, it can be directly connected or coupled to the otherelement or intervening elements may be present. In contrast, when anelement is referred to herein as being “directly connected” or “directlycoupled” to another element, there are no intervening elements present.

Although the terms “first”, “second”, etc. may be used herein todescribe various elements, components, regions, layers, sections and/orparameters, these elements, components, regions, layers, sections and/orparameters should not be limited by these terms. These terms are onlyused to distinguish one element, component, region, layer or sectionfrom another region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present inventive subject matter.

The terms “sheet,” “film,” “element,” “layer,” “component,” “section,”and “region” are used herein to describe a region of a material, and theuse of one term over another should not limit the scope of theembodiment. The use of the term sheet or film is ambiguous, for example,across different industries and something that may be considered a filmin one industry may be a sheet in another industry. Similarly, a devicemay have a scattering region that is a film. Thus, a sheet, film,element, layer, component, section and region discussed in an embodimentof this invention could also be termed a sheet, film, element, layer,component, section or region without departing from the teachings of thepresent inventive subject matter.

Furthermore, relative terms, such as “lower” or “bottom” and “upper” or“top,” may be used herein to describe one element's relationship toanother elements as illustrated in the Figures. Such relative terms areintended to encompass different orientations of the device in additionto the orientation depicted in the Figures. For example, if the devicein the Figures is turned over, elements described as being on the“lower” side of other elements would then be oriented on “upper” sidesof the other elements. The exemplary term “lower”, can therefore,encompass both an orientation of “lower” and “upper,” depending on theparticular orientation of the figure. Similarly, if the device in one ofthe figures is turned over, elements described as “below” or “beneath”other elements would then be oriented “above” the other elements. Theexemplary terms “below” or “beneath” can, therefore, encompass both anorientation of above and below.

The expression “illumination” (or “illuminated”), as used herein whenreferring to a light source, means that at least some current is beingsupplied to the solid state light emitter to cause the solid state lightemitter to emit at least some light. The expression “illuminated”encompasses situations where the light source emits light continuouslyor intermittently at a rate such that a human eye would perceive it asemitting light continuously, or where a plurality of solid state lightemitters of the same color or different colors are emitting lightintermittently and/or alternatingly (with or without overlap in “on”times) in such a way that a human eye would perceive them as emittinglight continuously (and, in cases where different colors are emitted, asa mixture of those colors).

A “luminophor” emits light when it becomes excited. The expression“excited” means that at least some electromagnetic radiation (e.g.,visible light, UV light or infrared light) is contacting the luminophor,causing the luminophor to emit at least some light. The expression“excited” encompasses situations where the luminophor emits lightcontinuously or intermittently at a rate such that a human eye wouldperceive it as emitting light continuously, or where a plurality ofluminophors of the same color or different colors are emitting lightintermittently and/or alternatingly (with or without overlap in “on”times) in such a way that a human eye would perceive them as emittinglight continuously (and, in cases where different colors are emitted, asa mixture of those colors).

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this inventive subject matterbelongs. It will be further understood that terms, such as those definedin commonly used dictionaries, should be interpreted as having a meaningthat is consistent with their meaning in the context of the relevant artand the present disclosure and will not be interpreted in an idealizedor overly formal sense unless expressly so defined herein. It will alsobe appreciated by those of skill in the art that references to astructure or feature that is disposed “adjacent” another feature mayhave portions that overlap or underlie the adjacent feature.

The present invention provides an improved light guide and lightemitting device with inherently more flexibility for display systemdesigners, light fixture or light emitting device designers, higheruniformities, and higher optical efficiency. In one embodiment of thisinvention, a lightguide comprises a low refractive index region disposedbetween light extracting region and a non-scattering region. In furtherembodiment of this invention, volumetric scattering lightguide comprisesa low refractive index region disposed between a volumetric scatteringregion and a non-scattering region. In one embodiment of this invention,a light emitting device comprises a volumetric scattering lightguidecomprising a non-scattering region, and a volumetric scattering regionseparated from the non-scattering region by a low refractive indexregion. In one embodiment, the low refractive index region prevents afirst angular range of light from entering into the volumetric lightscattering region of the volumetric scattering lightguide such that lesslight is directly scattered from the volumetric scattering region out ofthe lightguide near to the edge. A low refractive index material or filmdisposed on the surface of a non-scattering region of a lightguide canreduce the critical angle and cause high angle light that wouldotherwise transfer into the volumetric scattering region to reflect atthe interface between the non-scattering region and the low refractiveindex region.

In one embodiment of this invention, reducing the high angle lightprevents direct light from reaching the volumetric scattering film andenables a more uniform light emitting surface of the lightguide or lightemitting device. In this embodiment, by reducing the amount of directlight from the light source that reaches the volumetric scattering film,the film is illuminated more with indirect or scattered light. Forexample, the light which would have otherwise traveled into thevolumetric light scattering region and scattered leaving a brightnon-uniformity, is reflected with the addition of a low refractive indexregion back into the lightguide where it may be subsequently scatteredor reflected such that the light is further spread spatially and/orangularly. This can result in a more uniform distribution of light fluxreaching a specific region of the volumetric light scattering region. Inanother embodiment of this invention, the low refractive index regionincreases at least one of the illuminance at a plane perpendicular tothe light emitting device optical axis, luminance macro-uniformity, andluminance micro-uniformity of the light emitting device output surface.In another embodiment of this invention, the low refractive index regionincreases at least one of the average angular luminous intensity oraverage luminance of the light emitting device output surface.

In another embodiment of this invention, the use of a low refractiveindex region optically coupled between a non-scattering region and ascattering region of a volumetric scattering lightguide permits the useof a stronger diffuser or volumetric light scattering region (one with alarger angular FWHM intensity profile) while maintaining or increasingthe luminance uniformity or optical efficiency of a similar lightemitting device without a low refractive index region. In one embodimentof this invention, the stronger diffuser couples more light out of thelightguide and the optical efficiency of the lightguide or lightemitting device is at least 70%.

In one embodiment of this invention, the lightguide comprises at leastone type of spheriodal, substantially spheriodal, ellipsoidal,asymmetrically shaped, and non-spheriodal dispersed phase domains. Inone embodiment of this invention, a volumetric scattering lightguidecomprises a low refractive index region disposed between anon-scattering region and a volumetric light scattering region. Inanother embodiment of this invention, a surface relief scatteringlightguide comprises a low refractive index region disposed between anon-scattering region and a surface relief light scattering region.

In one embodiment of this invention a light guide containingsubstantially aligned asymmetric particles more efficiently controls thelight scattering in a light emitting device. One or more regionscontaining asymmetric particles may be used and the particle sizes mayvary between 2 and 100 microns in the smaller dimension. The lightscattering regions may be substantially orthogonal in their axis ofalignment. Alternatively, one or more asymmetrically scattering filmscan be used in combination with a backlight light guide and a reflectorto produce an efficient backlight system. The light guides may bemanufactured by embossing, stamping, or compression molding a lightguide in a suitable light guide material containing asymmetric particlessubstantially aligned in one direction. The light scattering light guideor non-scattering light guide may be used with one or more lightsources, collimating films or symmetric or asymmetric scattering filmsto produce an efficient backlight that can be combined with a liquidcrystal display or other transmissive display. By maintaining morecontrol over the scattering, the efficiency of the recycling of light byusing reflective polarizers can also be increased.

The non-spherical or spherical particles can be added to the matrixmaterial during processing or they can be created during manufacturing.In one embodiment of this invention, particles not substantiallyasymmetric in shape may be stretched along an axis after coating orduring or after an extruding process such that they become asymmetric inshape. Other methods for achieving a single region of non-sphericalparticles in a region are disclosed in U.S. Pat. No. 5,932,342, the textof which is incorporated herein by reference. By using multiple layersor multi-region methods such as co-extrusion, optical lamination,optical coupling, thermal bonding, multiple regions containing lightscattering particles can be combined into a single light scatteringelement. The degree of stretching can control the asymmetry and thusachieve a desired level of asymmetric light scattering. The asymmetricparticles may have a large variation in size depending on the desiredlevel of asymmetry. Methods including co-extrusion, laminating, thermalbonding, etc., can be used to achieve multiple regions containingdispersed phases with improved optical performance. The dispersed phasematerial may blended with the continuous phase material in a compoundingstep, a tumbling mixer, in a solvent blending process, or within anextruder.

In one embodiment of the invention, the asymmetric particles in thelight guide are obtained by reducing particles in size in the x, y orother directions by stretching a film after or during extrusion.

In one embodiment of this invention the particles have a refractiveindex n_(p1) different from the host matrix material refractive indexn_(h1) defined by at least one of |n_(mx1)−n_(px1)|≧0.001,|n_(my1)−n_(py1)|≧0.001, or |n_(mz1)−n_(pz1)|≧0.001 to providesufficient light scattering. The differential refractive index (Δn_(MP))defined as the absolute value of the to difference between the index ofrefraction of the matrix (n_(M1)) and the index of refraction of theparticles (n_(P1)), or |n_(M1)−n_(P1)|, may be from about 0.005 to about0.2, and preferably is from about 0.007 to about 0.1 in the x, y, or zdirections.

When more than one type of particles are used within a light diffusingsheet, they may have a refractive index n_(p2) in the x, y, or zdirection that is the same or different to that of the continuous phaseor the dispersed phase refractive index.

The asymmetric features, e.g., micro-bodies, typically are all orientedwith their major axes substantially in one direction in the plane of thesurface of the material. Desirably, the particles are made from amaterial which is capable of being deformed at a processing temperaturein order to create their non-spherical shape by stretching. The shapemay resemble a non-spherical ellipsoid or shapes that have non-constantradii in the x, y, or z direction may also be formed. For example, thedomains may appear randomly shaped in one plane (amoeba-like) andsubstantially planar in a perpendicular plane. Further, the volumedensity of the particle, the average size and shape, and the index ofrefraction in the x, y, and z directions may be optimized to controldesired properties of the light guide.

The average dimension of a dispersed domain or particle in the x, y, orz direction in the matrix may be from about 1 μm to about 30 μm,preferably from about 2 μm to about 15 μm, and most preferably fromabout 2 μm to about 5 μm in the minor dimension.

The average dimension of a dispersed domain or particle in the x, y, orz direction in the matrix may be from about 2 μm to about 2 cm,preferably from about 5 μm to about 1 cm, and most preferably from about10 μm to about 500 μm in the major dimension.

The differential refractive index (Δn_(ME)) is defined as the absolutevalue of the difference between the index of refraction of the matrix(n_(M)) and the index of refraction of the substantially spheroidal orellipsoidal particles (n_(E)), or |n_(M)−n_(E)|, may be from about 0.005to about 0.2, and preferably is from about 0.007 to about 0.1 in the x,y, or z direction.

Suitable materials for the particles include acrylics such aspolymethylacrylates; polystyrenes; polyethylenes; polypropylenes;organic acid cellulose esters such as cellulose acetate butyrates,cellulose acetates, and cellulose acetate propionates; polycarbonates;or silicones. The particles may also contain coatings of higher or lowerrefractive index materials, or they may be hollow materials containing agas mixture such as air. In a preferred embodiment, polyethylene may beused.

Other suitable materials for the transmissive micro-bodies include thosethat are not deformed during the extrusion or manufacturing process.These include spherical or non-spherical materials that have fibrous,plate-like or other orientable shapes. These include inorganic fibrousmaterial, glass fibers, mica, silica, cross-linked polymers, plate-likematerials, fibrous polymer materials with high melting points or highglass transition temperatures The micro-bodies may be aligned during themanufacturing process, such as alignment due to stretching or extrudingthe region containing the dispersed micro-bodies.

The light guide may also contain a surface relief structure on one ormore surfaces of the light transmitting material. The asymmetric surfacerelief structure can be manufactured by techniques as described above,e.g., embossing. The surface relief desirably contains asymmetricallyshaped features predominantly aligned in the horizontal or verticaldirections such that they refract, diffract, scatter, diffuse theincident light in the horizontal or vertical directions.

The surface relief structure of the light guide may help reflect,diffract, refract, or scatter light into or out of the light guide.Alternatively, the surface relief structure of the light guide maycollimate light (bring it toward smaller angles towards the displaynormal for example).

By using a vertically-oriented prismatic array as the surface reliefstructure light exiting the lightguide may be collimated in one plane.In one embodiment, the asymmetric microbodies are oriented horizontally(i.e., perpendicular to the lenticules) so the scattering issubstantially in the vertical direction (i.e., parallel to thelenticules). Thus, in this embodiment, the collimated light is focusedthrough the non-spherical particles with the light scattering only inthe vertical direction.

The alignment of the asymmetric micro-bodies can also vary. By aligningthe particles with respect to the prismatic structure at angles otherthan parallel or perpendicular, other asymmetric viewing angles can beachieved. The asymmetric micro-bodies will inevitably cause somescattering in the minor axis. This may be designed to be very small, orsignificant. In one embodiment, the scattering in the minor axis ischosen to be just sufficient to diffuse the specular component of thelight source in the plane perpendicular to major axis of the prismaticstructure.

Multiple-element diffusers in accordance with the invention aredesirably optically coupled to one another, i.e., so the intensity oflight passing from one region to the other is not substantially reduceddue to Fresnel interfacial reflection losses due to differences inrefractive indices between the regions. Optical coupling methods includejoining two regions having similar refractive indices, or by using anoptical adhesive with a refractive index substantially near or inbetween the elements or layers.

Particles that are significantly smaller than the wavelength of lightmay be added to alter the effective refractive index. In one embodiment,the size of the particles are less than 1/10^(th) the wavelength oflight. In a preferred embodiment, the size of the particles are lessthan 1/20^(th) the wavelength of light of interest such that significantadditional scattering (forward or backward) does not take place. Theseparticles may be symmetric, asymmetric, or random in shape. For example,very fine particles of titanium dioxide may be added to a material toincrease the effective refractive index of the material. The effectiverefractive index change can adjust the scattering properties of thematerial, refractive properties, and the interfacial reflections.

The diffusers of the invention may also include an optional hardcoat toincrease the stability of the element, and/or an optionalanti-reflective coating. The hardcoat may be any light-transmissivesupport layer, such as a siloxane-based polymer layer.

With embodiments of this invention, several steps in the light guidemanufacturing process and additional components can be eliminated. Inseveral embodiments, there is no need for any printing steps (i.e., nowhite dots) and a diffusion sheet that typically rests on top of thelight guide to smooth out the non-uniformities caused by the white dotsmay not be needed.

Light Emitting Device

In one embodiment of this invention, a lightguide is arcuate in shapeand comprises a low refractive index region and at least one of a lightextraction surface features and a volumetric light scattering region. Ina further embodiment, the lightguide is tapered in a first direction. Ina further embodiment of this invention, a light emitting devicecomprises a lightguide with at least one quadric surfaces. In oneembodiment of this invention, a light emitting device comprises at leastone light source and at least one arcuate lightguide. In a furtherembodiment of this invention, a light emitting device comprises alightguide with at least one inflection point on the light outputsurface. In a further embodiment of this invention, a light emittingdevice comprises two or more lightguides, two or more light sources anda volumetric light scattering region.

In one embodiment of this invention, a light emitting device comprisesat least one light source, an arcuate lightguide, a low refractive indexregion, and a volumetric light scattering element. In another embodimentof this invention, a light emitting device comprises a light source, alow refractive index region, and an arcuate lightguide with lightextraction features on the surface or within the volume of thelightguide. In a further embodiment on this invention, a light emittingdevice comprises a light source and a lightguide comprising a lowrefractive index region and at least one selected from the group oflight reflecting element or region, volumetric light scattering elementor region, anisotropic light scattering element or region, surfacerelief scattering element or region, light redirecting element orregion, lenticular lens element or region, light filtering directionalcontrol element or region, electrical components, light scattering lens,additional lightguides, light transmitting regions, light blockingregions, thermal transfer element, adhesives, mounts, housing, control,sensing or power electronics.

In one embodiment of this invention, more than one light emittingmodules are combined to form a light emitting device to provide at leastone of increased light output, increased light emitting surface area,increased illuminance in a specific region or angular range, increasedilluminance or luminance uniformity, additional illumination levels,additional illumination colors, additional functionality of the lightemitting device.

Light Emitting Device Application

In one embodiment of this invention, a light emitting device illuminatesan object, area, region, person, place, or volume of space. That is, alight emitting device can be a device which illuminates an area orvolume, e.g., a structure, a swimming pool or spa, a room, a warehouse,an indicator, a road, a parking lot, a vehicle, signage, e.g., roadsigns, a billboard, a ship, a toy, a mirror, a vessel, an electronicdevice, a boat, an aircraft, a stadium, a computer, a remote audiodevice, a remote video device, a cell phone, a tree, a window, an LCDdisplay, a cave, a tunnel, a yard, a lamppost, or a device or array ofdevices that illuminate an enclosure, or a device that is used for edgeor back-lighting (e.g., back light poster, static display sign, dynamicdisplay sign, other signage, displays, LCD displays), an organic LEDlight emitting device, bulb replacements (e.g., for replacing ACincandescent lights, low voltage lights, fluorescent lights, etc.),lights used for outdoor lighting, lights used for security lighting,lights used for exterior residential lighting (wall mounts, post/columnmounts), luminaires, wall-washers, ceiling fixtures/wall sconces,soffits, valances, coves, recessed fixture, torchiere, pendants, undercabinet lighting, lamps (floor and/or table and/or desk), landscapelighting, yard lights, path lights, track lighting, task lighting,specialty lighting, ceiling fan lighting, archival/art display lighting,street lamps, night lights, high vibration/impact lighting—work lights,etc., mirrors/vanity lighting, flashlights, torches, direct/indirectillumination devices, a combination of two or more of the aforementionedlight emitting devices and other similar and commonly used illuminationor light emitting devices. The light emitting device may provide directlighting, indirect lighting, both direct and indirect lighting, shieldedlighting, task lighting, down lighting, spot lighting, flood lighting,off-axis lighting, architectural lighting and may be edge-lit type,back-lit or direct-lit type, front-lit or combination thereof. In oneembodiment of this invention, the light emitting device is a replacementfor a fluorescent bulb. In one embodiment of this invention, the lightemitting device is a replacement for a an incandescent screw-type bulbsuch as an Edison screw-type socket incandescent light bulb. In oneembodiment of this invention, the light emitting device comprisesconfigurations and components used for LED replacement of fluorescentbulbs such as described in U.S. Pat. No. 7,049,761, the contents ofwhich are incorporated by reference herein.

In one embodiment of this invention, the light emitting device ismulti-functional and can perform multiple functions. For example, an LEDand illumination optic light emitting device in a mobile phone may beused as an illuminating flashlight, an autofocus flash for a built-incamera, and a flash for the digital photograph. In another example, thelight emitting device may provide illumination as well as provideinformation. For example, a dynamic sign (such as a digital sign withLEDs or with an LCD) or static display sign may provide information aswell as illumination. The light emitting device can provide functions inaddition to illumination by adding additional elements such as fans, CDracks, security alarms, emergency lighting electronics, mirrors,emergency exit signs, entertainment or disco lights. A light emittingdevice may comprise other elements not specifically described hereinthat may be understood to those in the field of illumination, opticalsignal communication, sign and display backlighting industries andlighting industry to facilitate or enhance the illumination orcommunication function or provide a specific function known to beachievable in combination with illumination.

The light emitting device may further comprise electrical elements toprovide power, control or other electrical based functions such aswires, sockets, switches, ballasts, connectors, circuitry, sensors, orpower generation elements such as batteries, solar panels, turbines,etc. It can contain optical elements to direct or spread the light suchas diffusers, prismatic elements, substrates, lightguides, lightredirecting elements, light transmitting materials, reflectors,reflective elements, louvers, flutes, elevating prisms, depressingprisms, female prisms, scattering elements, diffusive housings, supportelements and other housing elements which can include assemblycomponents such as screws, clips, connectors, and protective elementsand heat sinks.

Light Source

In one embodiment of this invention, the light emitting device comprisesat least one light source selected from the group of: fluorescent lamp,cylindrical cold-cathode fluorescent lamp, flat fluorescent lamp, lightemitting diode, organic light emitting diode, field emissive lamp, gasdischarge lamp, neon lamp, filament lamp, incandescent lamp,electroluminescent lamp, radiofluorescent lamp, halogen lamp,incandescent lamp, mercury vapor lamp, sodium vapor lamp, high pressuresodium lamp, metal halide lamp, tungsten lamp, carbon arc lamp,electroluminescent lamp, laser, photonic bandgap based light source,quantum dot based light source and other solid state light emittersincluding inorganic and organic light emitters. Examples of types ofsuch light emitters include a wide variety of light emitting diodes(inorganic or organic, including polymer light emitting diodes (PLEDs)),laser diodes, thin film electroluminescent devices, light emittingpolymers (LEPs), a variety of each of which are well-known in the art.In one embodiment of this invention, the light source is a transparentOLED such as those produced by Universal Display Corporation. In afurther embodiment of this invention, at least one of the lighttransmitting regions (or material) comprises a phosphor orphosphorescent material and the light source emits light capable ofexciting the phosphor. In one embodiment of this invention, the lighttransmitting region contains at least one phosphor material such thatsubstantially blue or UV light from at least one LED incident on thephosphor will cause the phosphor to emit light which will besubstantially collimated or directed by the lenticular lens array orbeads. By using a phosphor material in the light transmitting regionswhich will effectively convert the wavelength and transmit light, thebacklight can be made more uniform by light recycling and reflectionfrom the light reflecting regions of a optical composite and the outputwill direction will be efficiently controlled. In one embodiment of thisinvention, a light emitting device comprises an organic light emittingdiode (OLED) and a optical composite where the angular width of theoutput of the backlight is less than the angular width of the output ofthe OLED light source.

Multiple Light Sources

More than one light source may be used in an array, grouping orarrangement where the source types, spectral output, color, angularoutput, output flux, spatial locations or orientations of the lightsources may vary in one or more directions, planes or surfaces in apredetermined, random, quasi-random, regular or irregular manor. In oneembodiment of this invention, the light emitting device comprises morethan one light source arranged in at least one pattern selected fromlinear array, co-linear arrays, cylindrical arrays, spherical arrays,circular array, two-dimensional array, three-dimensional array, varyingheight array, angle of orientation varying array, opposing arraysoriented in substantially opposite directions and arrays oriented alonga surface. Arrays of light sources such as LEDs can be configured asdisclosed in U.S. Pat. No. 7,322,732, and U.S. patent application Ser.Nos. 12/017,600, 12/154,691, 11/613,692, the contents of each areincorporated by reference herein.

In one embodiment of this invention, a light emitting device comprisesan array of light sources disposed on at least one of a circuit board,connecting surface, flexible connecting surface, heat-sink, metalsubstrate, copper substrate, aluminum substrate, lightguide, or polymersubstrate.

In one embodiment of this invention, a light emitting device comprisesan LED array on a flexible circuit disposed in a circular or arc shapein proximity to a lightguide. In one embodiment of this invention, alight emitting device comprises a circular array of LED's on flexiblecircuit such that the light from the LED's is directed inward toward thecenter of a circular disc-shaped lightguide comprising light extractionelements of at least one type selected from the group of embossedfeatures, laser-ablated features, stamped features, inked surfacepatterns, injection molded features, etched surface patterns, sand orglass-blasted micro-patterns, uv cured embossing patterns, dispersedphase particle scattering, scattering from region comprising beads,fibers or light scattering or diffracting shapes. In one embodiment ofthis invention, the light emitting device further comprises a lightfiltering directional control element. In one embodiment of thisinvention, the light emitting device can perform as a downlight whereinthe fixture has a substantially circular disc-like shape.

Light Source Optics

The light source in accordance with one embodiment of this invention,comprises at least one light source optics of the type: die structureextraction optics such as photonic bandgap structures or structures onthe surface of a light emitting region that have a dimension in at leastone direction less than 1 micron in size, encapsulation lens, primaryoptics, secondary optics, reflective cavity surfaces, refractive lens,TIR reflector, diffractive optic, holographic optic, light shapingoptic, metallic reflector, integrator, refractive lens; reflective lens;hybrid lens, no light source optics, or other optical directioncontrolling features. Other optical elements that may be used with lightsources include reflective optical elements for semiconductor lightemitting devices such as those discussed in U.S. Pat. Nos. 7,118,262,7,456,499, and 7,280,288 the contents of each are incorporated byreference herein.

Light Source Duty Cycle

In one embodiment of this invention, a light emitting device comprises alight source that is pulsed over a defined period of time. Due to theresponse and recovery time of the human eye, a pulsed light source canappear to be continuously on. In certain drive schemes, this can enablea light source to appear to provide a comparable luminance orilluminance to the same light source driven continuously while usingless electrical power. Drive schemes and light source properties forpulsing may be designed for reduce power as described in U.S. patentapplication Ser. No. 11/755,162, the contents of which are incorporatedby reference herein.

Light Source Polarization

In one embodiment of this invention, at least one light source emitslight that is substantially non-polarized. In a further embodiment ofthis invention, at least one light source emits a first portion of lightsubstantially polarized in one polarization state. The polarizationstate of all or a portion of the light may be linearly polarized,elliptically polarized, circularly polarized or a combination thereof.In one embodiment of this invention, the orientation of the polarization(or light source) is configured along a first polarization axis. Thefirst polarization axis (or light source) may be aligned parallel,perpendicular, or at an angle σ, with respect to at least one of theoptical axis of the light emitting device, the optical axis of the lightsource, the normal to the light emitting output surface, the edge orsurface of an element (optical element or otherwise such as a mechanicalmount) of the light emitting device, or the edge or surface of an objectof illumination such as a desk, hallway floor, window, etc. In oneembodiment of this invention, a light emitting devices emits polarizedlight through the use of an absorptive polarizer, reflective polarizer,multi-layer reflective polarizer, wire-grid polarizer, cholestericliquid crystal layer, or from a light source such as an LED, OLED, orother light source that emits polarized light such as disclosed in U.S.patent application Ser. Nos. 10/942,090, 11/209,905, 10/202,561 and U.S.Pat. Nos. 6,122,103, 6,018,419, 6,297,906, 6,396,631, 5,783,120,3,069,974, 6,101,032, 6,141,149, 6,947,215, and 5,594,830, the contentsof each are incorporated by reference herein.

Light Source Spectral Output

In one embodiment of this invention, a light emitting device compriseslight sources wherein the spectral output the light source or group ofsources may be narrowband or broadband. The light source color may be aprimary color, non-primary color, white, cool white, warm white or othercolor in the visible, ultraviolet, or infrared spectrum. Variouscombinations of light sources of different spectral properties may beused to provide desired spectral output in an angular range or spatialregion or for all or a portion of the total light output of the lightemitting device. Combinations of different spectral sources in a lightemitting device include those discussed in U.S. Pat. Nos. 5,803,579 and7,213,940, and U.S. patent application Ser. Nos. 11/936,163, 11/951,626,the contents of each are incorporated by reference herein.

In one embodiment of this invention, the light source emits light of asubstantially single color (a full wavelength bandwidth at have maximumintensity of less than 40 nanometers for example). In another embodimentof this invention, the light emitting device (or the light source withina light emitting device) includes a light emitting region and awavelength conversion material such as a luminophor. The luminophor maybe a fluorophore, a phosphor, or other chemical compound that manifestsluminescence such as transition metal complexes (rutheniumtris-2′2′-bipyridine). In another embodiment of this invention, a lightemitting device comprises at least one wavelength conversion materialthat is a non-linear optical material such that a first portion ofincident light undergoes second harmonic generation (SHG), sum frequencygeneration (SFG), third harmonic generation (THG), difference frequencygeneration (DFG), parametric amplification, parametric oscillation,parametric generation, spontaneous parametric down conversion (SPDC),optical retification, or four-wave mixing (FWM). Examples of non-linearoptical materials are known in the photonics industry and includepotassium niobate, lithium iodate, gallium selenide. Other materials andcomponents useful for converting light of one wavelength range to asecond wavelength range such as quantum dots, nanodots, nanoparticles,quantum well devices, and semiconductor materials with confinedexcitons. The wavelength conversion material may be located in or on oneor more surfaces or elements within the light emitting device or withinthe light source packaging, such as a phosphor material deposited on orin a light scattering lens of a light emitting device or deposited nearthe die of an LED or within the LED package. Alternatively, thewavelength conversion material may be located remotely or outside thelight source packaging, as in the case of some remote phosphors andphosphor films.

Optical Axis of the Light Source

The optical axis of the light source, as used herein, is the directionof the peak intensity of the light emitting from the light source. Withcommonly used LEDs, for example, this direction is typically normal to apackaging or mounting surface of the package. However, in cases wherethe light source emits light at an angle from the normal to the typicalmount surface, the optical axis is the angle (or angular range) at whichthe peak intensity output occurs. For example, in side emitting LEDssuch as the LXHL-FW3C white side-emitting LED from Philips LumiledsLighting Company, the light is emitted substantially radiallysymmetrically at an angle of approximately 82 degrees. In this example,the optical axis of the LED is 82 degrees from the normal to the outputsurface. In a configuration where the light output profile of the lightsource is not symmetric, the optical axis, for the purposes of theembodiments and configurations disclosed herein is the direction orangular range of the peak intensity. The direction may include anangular range such as phi or theta of 82 degrees in polar coordinates.The optical axis of the light source does not necessarily align with anedge, mounting surface, or center of the light output surface of thelight source. In one embodiment of this invention, at least one lightsource or optical axis of the light source of the light emitting deviceis aligned parallel, perpendicular, or at an angle, ρ, with respect toat least one of the optical axis of the light emitting device, theoptical axis of a second light source, the normal to the light emittingsurface, the edge or surface of an element (optical element or otherwisesuch as a mechanical mount) of the light emitting device, or the edge orsurface of an object of illumination such as a desk, hallway floor,window, or wall. In one embodiment of this invention, the optical axisof the light source in the light emitting device intersects the lightemitting output surface of the light emitting device. The light emittingoutput surface may be a light scattering lens, a surface of thelightguide, a surface of a volumetric light scattering element, asurface relief region, a light extracting region or other element of thelight emitting device. The optical axis of the light source may beparallel, perpendicular, or at an angle to another light source,lightguide, optical component or optical axis of the light emittingdevice.

Lightguide

In one embodiment of this invention, a light emitting device compriseslightguide. a lightguide is a region bounded by the condition that lightrays traveling at an angle that is larger than the critical angle willreflect and remain within the region. Thus, a lightguide region of amaterial or materials is capable of supporting a significant number ofmultiple internal reflections of light due to the refractive indexdifference between the material and the surrounding material. Typically,a lightguide is comprised of a polymer or glass and the surroundingmaterial is air or a cladding material with a lower refractive index.The lightguide may contain materials or regions within the volume thatwill scatter, reflect, refract, or absorb re-emit a first portion oflight into an angular condition such that it escapes the lightguide. Inone embodiment of this invention a volumetric scattering lightguide isan optical composite comprising more than one of the same or differentregions selected from the group of non-scattering region, volumetricscattering region, surface relief feature region, light extractionregion, light redirecting region, low refractive index region, lightoutput region, light input region or edge.

In one embodiment of this invention, a lightguide comprises asubstantially transparent, non-scattering polymer optically coupled to alow refractive index material in one or more regions. In anotherembodiment of this invention, a lightguide comprises a substantiallytransparent, non-scattering polymer optically coupled to a lightscattering material in one or more regions. The light scatteringmaterial can be a volumetric scattering region or film, a surface reliefregion or film, or a combination thereof. In another embodiment of thisinvention, the lightguide is a film or sheet comprising a matrixmaterial and light scattering domains dispersed substantially throughoutthe film or sheet. In another embodiment of this invention, thelightguide comprises a substantially non-scattering region and avolumetric light scattering region, or other combination of regions asdiscussed in U.S. patent application Ser. Nos. 11/426,198, 11/848,759,11/957,406, 12/122,661 and U.S. Pat. Nos. 7,431,489, 7,278,785,6,924,014, 6,379,016, 5,237,641, and 5,594,830, the contents of each areincorporated by reference herein. In one embodiment of this invention, alight emitting device comprises a “hollow lightguide”. Examples of“hollow lightguides” are discussed in U.S. Pat. No. 6,481,882, thecontents of which are incorporated by reference herein. In anotherembodiment of this invention, a light emitting device comprises a flutedlightguide. Examples of fluted lightguides are discussed in U.S. Pat.No. 6,481,882, the contents of which are incorporated by referenceherein. In another embodiment of this invention, a light emitting devicecomprises a lightguide with grooves or surface relief structures on atleast one surface. Examples of surface relief structures includinggrooves on lightguides are discussed in U.S. Pat. No. 7,046,905, thecontents of which are incorporated by reference herein. Other types oflightguides are known in the backlighting industry and optical fiberindustries.

Typically, a lightguide extends longer in a first direction than asecond direction orthogonal to the first. In these cases and in thenotation used herein, the length, L, is the dimension of the lightguidein the first direction and width, W, is the length of the dimension ofthe lightguide in the second direction orthogonal to the first. Thelight may enter the lightguide through any number or combination ofsurfaces of the lightguide. Light may enter through the edge(edge-surface), larger surface, or through a light coupling elementoptically coupled to one or more surfaces of the lightguide.

Lightguide Shape

The lightguide of one embodiment of this invention is substantiallyplanar in shape. In another embodiment of this invention issubstantially arcuate and curved along at least one direction. A curvedor arcuate lightguide includes lightguides wherein one or more surfaceshas a surface normal wherein the surface normal changes angle as onemoves along the surface. These can include continuously changingsurfaces or curves as well as discretely changing (sharp corners)transitions. The lightguide may be curved on two or more opposite facesor only on one face. The curved shape or surface includes those that canbe defined by a mathematical relationships such as f(x,y,z). Thecross-sectional side view of an arcuate surface (or portion of asurface) of a lightguide may illustrate an arc in two-dimensional formthat takes the shape of a full or partial circle, parabolic curve, conicsection, rational curve, or elliptic curve. In one embodiment of thisinvention, the dimensions of the lightguide in first and second mutuallyorthogonal directions are each greater than one selected from 5 times,10 times, 20 times, 30 times, and 50 times the dimension in a thirddirection orthogonal to the first and second mutually orthogonaldirections.

In one embodiment of this invention, a light emitting device comprisesan arcuate lightguide with a curved surface of a genus greater than oneselected from zero, one, two, or three. Curved surfaces with of a genusgreater than zero include doughnut like surfaces or stretched doughnutlike surface wherein a cutting along the closed curve does not result ina disconnected manifold

In a further embodiment of this invention, a light emitting devicecomprises an arcuate lightguide with a quadric surface. In oneembodiment of this invention, a light emitting device comprises alightguide wherein one portion of the surface of the lightguide isquadric and can be substantially represented by the equation (whencentered at the origin):

${{{\pm \frac{x^{2}}{a^{2}}} \pm \frac{y^{2}}{b^{2}}} \pm \frac{z^{2}}{c^{2}}} = 1.$

Surfaces that also resemble or closely approximate a quadric surface andsurfaces with imperfections or sub-regions that cause a surface todeviate from a perfect quadric surface are also deemed to be in thescope of this invention. In one embodiment of this invention, a lightemitting device comprises a lightguide wherein at least a portion of asurface of the lightguide (such as the light emitting output surface) isa quadric surface in the form selected from one of a full or partialellipsoid, spheroid, paraboloid, circular paraboloid, ellipticparaboloid, hyperbolic paraboloid, hyperboloid of one sheet, cone,elliptic cylinder, circular cylinder, or parabolic cylinder. In oneembodiment of this invention, a light emitting device comprises alightguide wherein two substantially opposing surfaces are quadric. Thelightguide may be rotationally symmetric about a first axis of symmetryor it may be non-symmetric in shape. In one embodiment of thisinvention, the lightguide or light emitting device comprising thelightguide is substantially bulbous in shape and may be used as a lightbulb. In another embodiment of this invention, the outer surface of alight bulb comprises a lightguide which is bulbous and shaped similar toan incandescent Edison type light bulb. In another embodiment of thisinvention, the lightguide or light emitting device comprising thelightguide is substantially rod-like or tube-like in shape and may beused as a replacement light source for a linear fluorescent light bulb.In another embodiment of this invention, the outer surface of a lightsource for replacing a linear fluorescent light bulb comprises alightguide which is substantially arcuate in a first direction andsubstantially linear in a second direction orthogonal to the firstdirection and shaped similar to a linear fluorescent light bulb. Inanother embodiment of this invention, light emitting device orlightguide output surface is shaped similar to an Edison typeincandescent light bulb, a parabolic aluminized reflector (PAR type)light bulb, an MR16 bulb, or a linear fluorescent bulb.

In a further embodiment of this invention, a light emitting devicecomprises a lightguide with a one or more inflection points on the lightemitting output surface or a surface opposite the light emitting outputsurface. An inflection point is a point on a surface or line wherein thecurvature changes sign. A lightguide surface wherein the surface normalis changing directions can cause an inflection point. An inflectionpoint on a surface or interface of a lightguide will reduce the angle ofincidence of light traveling in the lightguide on the interface (such asbetween the lightguide surface an air) and will increase the likelihoodof light escaping the lightguide. A lightguide may have more than oneinflection point and the points may be located in regions on or off ofthe light source optical axis or light emitting device optical axis.

Inflection points and tapers in a lightguide increase the amount oflight exiting the lightguide further away from the light source(relative to a non-tapered or lightguide without inflection points) bychanging the angle of the surfaces relative to the angles of the lighttraveling within the lightguide.

In a further embodiment of this invention, a light emitting devicecomprises a lightguide with a sagittal depth (Sag Depth or SD) greaterthan twice the edge thickness of the lightguide. The sag depth of alightguide is the distance from a flat plane at a given diameter of thelightguide to the furtherest point on a concave surface of thelightguide. The SD of a lightguide is shown in FIG. 12. For non-roundlightguides or polygonal lightguides, the sag depth of the lightguide isthe distance from the furtherest point on a concave surface of thelightguide to a flat plane comprising the opposite edges of the longerdimension (or length) of the lightguide. In another embodiment of thisinvention, a lightguide comprises a ratio of sag depth to edge thicknessof greater than one selected from 3, 4, 6, 10, 20 and 30. In anotherembodiment of this invention, a lightguide has a sag depth greater thanone selected from 5, 10, 20, 50, and 100 millimeters.

In another embodiment of this invention, a lightguide comprises anangularly extended surface. An angularly extended surface is one whereinthe maximum subtended angle comprising the surface between any point notlocated on the surface and any two points on the surface all in the sameplane is greater than 180 degrees. A planar lightguide or flat wedgelightguide does not comprise an angularly extended surface. A perfectlyhemispherical surface is not an angularly extended surface as themaximum subtended angle is exactly 180 degrees (for a point positionedat the center). In one embodiment of this invention, a lightguidecomprises an angularly extended surface that comprises more than onehalf of a closed spherical or ellipsoidal surface. A lightguide with anangularly extended surface may be used to increase the travelingdistance of light within the lightguide (such as for improving luminanceuniformity or color uniformity) without increasing the volume. Anangularly extended surface may curve back upon itself so that the lightsource edge could be located within the volume or be substantiallyenclosed by the lightguide. In one embodiment of this invention, a lightemitting device comprises an angularly extended lightguide wherein thelightguide curves back in on itself and light from a light sourceilluminates the lightguide simultaneously traveling in oppositedirections.

In one embodiment of this invention, the curvature of the lightguideredirects a portion of the output from a first region of the lightemitting region by rotating the angle of the exiting light in thedirection which the region of the surface from which it exited wasrotated relative to a flat, planar surface. For example, when a planarlightguide is curved (or angled) to form a concave lightguide relativeto the nadir, a portion of the light from the LEDs on the left side ofthe lightguide (light emitting device is directed downwards) which isextracted from the lightguide in the region near the left side of thelight extracting region is rotated to larger angles from the nadir thanthe output from a similar planar lightguide. Similarly, a portion of thelight from the LEDs on the right side of the lightguide which isextracted from the lightguide in the region near the right side of thelight extracting region is rotated to larger angles from the nadir thanthe output from a similar planar lightguide.

Light traveling in a lightguide, from left to right for example, mayencounter one or more curved boundary surfaces of the lightguide thatincrease or decrease the angle of incidence at the lightguide boundaryinterface relative to a planar lightguide. In one embodiment of thisinvention, the lightguide is curved or angled in a convex shape relativeto the nadir and a portion of the angular light output of the lightemitting device relative to that of a similar planar lightguide isdirected more toward the nadir in a first plane comprising the curvedshape. In a further embodiment of this invention, the lightguide iscurved or angled in a concave shape relative to the nadir and a portionof the angular light output of the light emitting device relative tothat of a similar planar lightguide is directed more away from the nadirin a first plane comprising the curved shape.

In a further embodiment of this invention, the light blocking region orother element of the light emitting device such as a housing or thermaltransfer element or heat sink reflects, absorbs, refracts or scatters aportion of light from a light emitting region of the light emittingdevice traveling at an angle selected from 40°, 50° 60°, 70° and 80°from the nadir.

In another embodiment of this invention, the light blocking region orother element of the light emitting device such as a housing or thermaltransfer element or heat sink reflects, absorbs, refracts or scatters aportion of light from a light emitting region of the light emittingdevice comprising a curved lightguide such that the luminance in anangular region from 55 degrees to 90 degrees from the nadir is less thanthe luminance at the same angle from the nadir of a similar lightemitting device with a planar, non-curved lightguide.

Lightguide Taper

In one embodiment of this invention, a light emitting device comprises atapered lightguide. In another embodiment of this invention, thelightguide comprises at least two surfaces that are not parallel to eachother. A tapered lightguide is one wherein the separation distancebetween two substantially opposing surfaces decreases in a firstdirection parallel to one of the surfaces within a region of thelightguide. A tapered lightguide includes lightguides with substantiallyplanar opposing surfaces (wedge-type) and lightguides where one or bothsurfaces has a cross-sectional curve shape in one or more directions. Inone embodiment of this invention, a lightguide may have a substantiallyplanar surface and an arcuate surface such that the lightguide tapers ina first direction parallel to one of the surfaces. A lightguide may betapered in a first taper direction and tapered in a second directionorthogonal to the first. In a further embodiment of this invention, alight emitting device comprises a lightguide wherein the separationdistance between two substantially opposing surfaces increases in afirst direction parallel to one of the surfaces within a region of thelightguide. In a further embodiment of this invention, a light emittingdevice comprises a lightguide that tapers and thickens in a firstdirection wherein the separation distance between two substantiallyopposing surfaces increases and decreases in a first direction parallelto one of the surfaces within a region of the lightguide. For example,the lightguide may be shaped similar to a biconvex lens where light iscoupled into the outer edge and the lightguide expands and then tapersas light progresses toward the opposite edge. In other example, thelightguide may be in a shape similar to a biconcave lens, where light iscoupled into the outer edge and the lightguide tapers and then expendsas the light progresses toward the opposite edge. Similarly, one or morelight sources may be disposed in the central region of a biconvex orbiconcave shaped lightguide wherein the lightguide tapers or expands,respectively, as the light travels from the center to the edge of thelightguide. Further examples included cylindrical lenses with abiconcave or biconvex cross-section in a first region.

In a further embodiment of this invention, a light emitting devicecomprises a lightguide that tapers in a first direction and thickens ina second direction orthogonal to the first direction.

Lightguide Input Edge

In one embodiment of this invention, the surface of the input edge of alightguide which receives the light from the light source is one ofcurved, lens-like, convex, concave, non-planar or parametric surfacewherein the angular orientation of the surface normal across the surfacechanges. In one embodiment of this invention, a light emitting devicecomprises a lightguide with an input surface with a concave regiondisposed adjacent to a light source. A concave surface disposed toreceive light from a light source such that the light from the lightsource is not refracted toward the optical axis of the light source inthe lightguide will spread faster within the lightguide, thus reducingthe mixing distance. The curvature may be in the length direction, widthdirection or both. In one embodiment of this invention, the input edgeof a lightguide is concave within a first plane parallel to the opticalaxis of the light source and convex within a second plane parallel tothe optical axis of the light source and perpendicular to the firstplane. In one embodiment of this invention, the input surface of thelightguide is illuminated by a plurality of light sources wherein thelight from the plurality of light sources cross paths within thelightguide.

Lightguide Output Edge

In one embodiment of this invention, the surface of the output edge of alightguide which receives the light from within the lightguide is one ofcurved, lens-like, convex, concave, non-planar or parametric surfacewherein the angular orientation of the surface normal across the surfacechanges. In one embodiment of this invention, a light emitting devicecomprises a lightguide with an output surface with a beveled edge. Abeveled edge can be used to refract the light remaining in thelightguide that has not been coupled out due to a diffuser, lightextraction features, taper, etc. By refracting the light from a bevel,the directionality of the light exiting the edge of the lightguide canbe controlled. In one embodiment of this invention, the edge is beveledat an angle less than 90 degrees from the first light output surface ofthe lightguide. In another embodiment of this invention, the output edgehas a first curved region. The curvature may be in the length direction,width direction or both. In one embodiment of this invention, the outputedge of a lightguide is concave within a first plane parallel to theoptical axis of the light emitting device and convex within a secondplane parallel to the optical axis of the light emitting device andperpendicular to the first plane. In a further embodiment of thisinvention, the lightguide output edge comprises a light reflectingelement. In another embodiment of this invention, the lightguide outputedge comprises a light redirecting element or a light scattering regionor element.

Lightguide Output

In one embodiment of this invention, a light emitting device comprises alightguide wherein the percentage of light flux exiting the lightguideon the surface closer to the light emitting device optical axis isgreater than the light flux exiting the lightguide on the oppositesurface further from the light emitting device optical axis. In oneembodiment of this invention, the light emitting device comprises alightguide wherein the percentage of light flux exiting the lightguidefrom a top output surface and the bottom output surface is selected froma group of 5%-15% and 95%-85%; 15%-30% and 85%-70%; 30%-50% and 70%-50%;50%-75% and 50%-25%; and 75%-95% and 25%-5%, respectively. In anotherembodiment of this invention, the percentage of light flux exiting thelight emitting device in a first direction from a first output surfaceand a second direction from a second output surface is selected from agroup of 5%-15% and 95%-85%; 15%-30% and 85%-70%; 30%-50% and 70%-50%;50%-75% and 50%-25%; and 75%-95% and 25%-5%, respectively. In anotherembodiment of this invention, the light emitting device comprises a thelightguide, a first light source disposed to direct light into the firstnon-scattering region through a first input surface, a first lightemitting device output surface, a second light emitting device outputsurface opposite the first light emitting surface, wherein thepercentage of light flux exiting the light emitting device from thefirst light emitting device output surface is greater than 50% and thepercentage of light flux exiting the light emitting device from thesecond light emitting device output surface is less than 50%. In afurther embodiment of this invention, the percentage of light fluxexiting the light emitting device from the first light emitting deviceoutput surface is greater than 60% and the percentage of light fluxexiting the light emitting device from the second light emitting deviceoutput surface is less than 40%. In another embodiment of thisinvention, the percentage of light flux exiting the light emittingdevice from the first light emitting device output surface is greaterthan 70% and the percentage of light flux exiting the light emittingdevice from the second light emitting device output surface is less than30%. In another embodiment of this invention, the percentage of lightflux exiting the light emitting device from the first light emittingdevice output surface is greater than 60% and the percentage of lightflux exiting the light emitting device from the second light emittingdevice output surface is less than 40%.

The first direction may be the up direction with the first outputsurface as the top surface and the second direction may be the downdirection with the second output surface as the bottom surface.

Lightguide Alignment

In one embodiment of this invention, a light emitting device comprises alightguide with an output surface oriented at an angle, ∈, to theoptical axis of the light emitting device. The angle ∈ may be chosensuch that the output surface is aligned substantially parallel,perpendicular, or at an angle to at least one of the optical axis of atleast one light source, the optical axis of the light emitting device,the light output plane of the light emitting device, and the axis ofluminous intensity glare cut-off In one embodiment of this invention, ∈is 0 degrees and the output surface of the lightguide is substantiallyparallel to the optical axis of the light emitting device. In a furtherembodiment of this invention, ∈ is 90 degrees and the output surface ofthe lightguide is substantially perpendicular to the optical axis of thelight emitting device. In a further embodiment of this invention ∈ isgreater than one selected from the group of 10 degrees, 30 degrees, 50degrees, 60 degrees and 70 degrees. In a further embodiment of thisinvention ∈ is less than one selected from the group of 10 degrees, 30degrees, 50 degrees, 60 degrees and 70 degrees. The orientation of thelightguide contributes to the angular optical output radiation of thelight emitting device. In one embodiment of this invention, orientingone or more lightguides at a smaller angle ∈ results in more light beingdirected toward the optical axis of the light emitting output device. Inanother embodiment of this invention, orienting one or more lightguidesat a larger angle ∈ results in more light being directed away from theoptical axis of the light emitting output device. This is particularlyuseful when trying to achieve specific off-axis radiation patterns suchas batwing profiles for light fixture designed to have indirect outputor for other light directing applications such as wall washing. Theorientation of the lightguide or portion of a lightguide, or onelightguide in a device comprising more than one lightguide can alsoprovide blocking of light that would normally exit the light emittingdevice at a glare angle such as light exiting the light emitting deviceat more than approximately 45 degrees.

In one embodiment of this invention, a light emitting device comprises alightguide aligned such that the plane perpendicular to the normal to asecond output region of the light emitting outer surface of thelightguide closer to the second input coupling edge of the lightguide isoriented at an angle, δ, to the optical axis of the light sourcedirected into the first light input coupling edge. In one embodiment ofthis invention, δ is greater than one selected from 50 degrees, 80degrees, 90 degrees and 100 degrees.

In one embodiment of this invention, a light emitting device comprisesmore than one lightguide wherein the lightguides are oriented at anangle, φ, with respect to each other. In one embodiment of thisinvention, the angle, φ, is in a range selected from the group: greaterthan 10 degrees; greater than 45 degrees; greater than 80 degrees;greater than 90 degrees; greater than 130 degrees; 0 degrees to 5degrees; 10 degrees to 30 degrees; 30 degrees to 45 degrees; 45 degreesto 60 degrees; 60 degrees to 90 degrees; and 90 degrees to 170 degrees.

In a further embodiment of this invention, a light emitting devicecomprises an arcuate lightguide with first and second light outputregions oriented at an angle φ3 with respect to each other on the outerlight output surface of the lightguide. In one embodiment of thisinvention, a light emitting device comprise a lightguide wherein thesurface normal of the light output surface of the lightguide varies in afirst plane. The surface of the lightguide may be substantiallyrotationally symmetric and the surface normal may vary around a lightemitting device output axis.

Lightguide Location

In one embodiment of this invention, the lightguide is disposed in anoptical path between the light source and at lease one of a an opticalfilm, light scattering element, light redirecting optical element, lightfiltering directional control element, light scattering lens, protectivelens, housing, mounting element, thermal transfer element, volumetriclight scattering element, a second lightguide, and a second lightsource.

Lightguide Composition

The lightguide of one embodiment of this invention is comprised of alight transmitting material. In another embodiment of this invention,the lightguide is comprised of a light transmitting material. selectedfrom thermoplastic polymer, thermoset polymer, plastic, glass, rubber,liquid, other light transmitting material, or a composite of two or moreof the aforementioned materials.

Elements of the Lightguide

In one embodiment of this invention, a light emitting device comprises alightguide which comprises at least one of a volumetric light scatteringregion, volumetric anisotropic light scattering region, low refractiveindex region, surface relief light scattering region, surface relieflight scattering region embedded within the volume, light reflectingelement, specularly reflecting light reflecting element, diffuselyreflecting element, forward scattering element, backward scatteringelement, light extraction features, tapered surface, curved surface,quadric surface, embedded light source, embedded LED, diffractingelement, holographic element, non-scattering regions, light redirectingelement, or light filtering directional control element. One or more ofthe aforementioned features or elements may be optically coupled to alight transmitting material in one or more predetermined regions. Theregion of coupling may be a continuous layer or it may be opticallycoupled in a predetermined pattern. The pattern may be regular, random,substantially random or regular or in a mathematically definablepattern. In one embodiment of this invention, the lightguide comprisesat least one output surface or light emitting surface wherein lightexits the lightguide. In a further embodiment of this invention, thelightguide comprises a light output surface and a first and second lightoutput region disposed near a first and second light input couplingedge, respectively. The lightguide may comprise more than one volumetriclight scattering region and the lightguide may be arcuate in shape suchthat the first and second light output regions are at an angle to eachother.

The lightguides may be composite materials such that they comprisemultiple layers with different functions are properties includingscattering, reflecting, selective light extraction, diffusing foruniformity, scattering at predetermined angular ranges, mixing for coloror uniformity or configuration. Multiple lightguides can be used in asingle light emitting device. Examples of lightguides and compositescomprising multiple layers and methods of manufacture include thosepresented in U.S. Pat. Nos. 7,278,775, 7,431,489, and U.S. patentapplication Ser. Nos. 11/426,198, 12/122,661, 12/198,175, 11/957,406,11/848,759, the contents of each are incorporated by reference herein.

Non-Scattering Region of the Lightguide

In one embodiment of this invention, a light emitting device comprises alightguide with a substantially non-scattering region. A non-scatteringregion may comprise a light transmitting material with a refractiveindex between 1.01 and 3. As used herein, a non-scattering region is aregion comprised of a light transmitting material where there is a lowamount of haze, high amount of clarity, or low angular FWHM intensitydiffusion angles of collimated light due to components within the volumeof the material. The amount of volumetric scattering for a region isdependent on the thickness of the region in a given direction and thenumber of scatterers or dispersed phase domains within the region andthe size and refractive index of the domains. While light travels inmore than one direction within a lightguide, measurements fordetermining a non-scattering region as used herein are taken in adirection substantially normal to the output surface of the lightguideor light emitting device. For example, the clarity, haze or diffusionangles of a 5 mm thick acrylic sheet lightguide approximately 60 cm×60cm will typically be measured in the thickness direction.

Haze is one method for measuring the amount of wide angle scattering inan element. In one embodiment of this invention, the haze of the of thenon-scattering region or element measured according to ASTM D1003 with aBYK Gardner Hazemeter is less than one selected from 5%, 10%, 20%, 30%,40%, and 50%.

Clarity is method for measuring the narrow angle scattering of a lightscattering element. In one embodiment of this invention, the clarity ofthe of the non-scattering region or element measured with a BYK GardnerHazemeter is greater than one selected from the group of 40%, 50%, 60%,70%, 80%, 90% and 95%.

A method of measuring the angular FWHM intensity diffusion angles ofcollimated light is by directing collimated visible laser light, at 532nm for example, and measuring the full angular width at half maximumintensity of the light passing through the thickness direction of thenon-scattering region. In one embodiment of this invention, the fullangular width at half maximum intensity of collimated 532 nm laser lightafter passing through a non-scattering region is less than on selectedfrom the group of 20 degrees, 10 degrees, 5 degrees, 3 degrees, and 1degree.

Non-Scattering Region Location

A lightguide may comprise more than one non-scattering region. Thenon-scattering region may be disposed between a light source and avolumetric or surface relief scattering region. A second non-scatteringregion may be disposed on the opposite side of the volumetric scatteringregion or surface relief scattering region than the first non-scatteringregion. In another embodiment of this invention, a lightguide comprisesa volumetric light scattering region disposed between two non-scatteringregions. The second non-scattering region may be disposed opticallycoupled to an optical element of the lightguide such that it is notoptically coupled to the first non-scattering region.

Light Extracting Region

In one embodiment of this invention, a light emitting device comprises alightguide with a light extraction region disposed on or within at leastone inner or outer light output surface or region of the lightguide. Thelighting region may comprise a surface relief region or a volumetricscattering region. In one embodiment of this invention, the lightextraction features of a light extracting region are disposed to receivelight from within the lightguide and direct a first portion of theincident light to an angle less than the critical angle at an outersurface of the lightguide. Light extraction features may typically bedescribed as surface relief light extraction features, volumetric lightextraction features (typically volumetric scattering region), or somecombination thereof. Light extraction surface features may includenon-planar modifications or additions to a surface. An example of addinglight extraction features include screenprinting translucent or lightscattering ink features on the surface of the lightguide such astitanium dioxide or barium sulfate or beads dispersed in a methacrylatebased ink or binder. In the example of adding beads in a bindingmaterial to the surface of a non-transmitting region, if the beads havea refractive index substantially the same as the binder, then the regionmay be considered a surface relief light extraction feature. If thebeads have a refractive index different from the binder, then thecoating is a surface relief and volumetric light extracting feature dueto the scattering within the binder from the beads and the non-uniformsurface created by the beads within the coating.

An example of a subtractive modification to a surface to achieve lightextraction features includes laser ablation of a PMMA substrate toachieve pits or ridges in a surface to scatter, reflect, diffract, orrefract incident light from within the lightguide. Other lightextraction features included injection molded surface features, embossedfeatures into the surface, optically coupling surface-relief films tothe lightguide, optically coupling volumetric light scattering regionsor films to the lightguide, insert molding optical elements or diffuserfilms to the lightguide, extruding or casting or injection molding alightguide comprising light scattering domains within the volume,mechanically or etching or scribing features into the lightguide,abrading features into the lightguide, sandblasting features, printingfeatures, photopolymerizing or selective polymerizing of features into alayer or coating, and other methods known in the art of backlights fordisplays for achieving light extraction from a lightguide. Volumetric orsurface relief light scattering elements can be comprised of lighttransmitting or reflecting materials. Surface relief light scatteringregions may comprise one or more lenses, refractive elements orfeatures, reflective elements or features, diffracting elements orfeatures, scattering elements or features or other surface relieffeatures or deviations from a planar surface known to redirect a firstportion of light. One or more light extraction surface relief featuresmay contain protrusions or pits that may range from 1 nm to 10 mm in thex, y, or z directions. The profile or individual features may haveperiodic, random, semi-random, or other uniform or non-uniformstructure. The surface features may be designed to provide functions tothe light redirecting element, such as collimation, anti-blocking,refraction, lightguide output coupling or extraction, symmetricdiffusion, asymmetric diffusion or diffraction. In some embodiments, thesurface features are a linear array of prismatic structures that providecollimation properties. In another embodiment, the surface includeshemispherical protrusions that prevent wet-out or provide anti-blockingproperties or light-collimating properties. In another embodiment ofthis invention, the light extraction features are holographic ordiffractive features that redirect a first portion of incident light. Ina further embodiment of this invention, a lightguide comprises a lightextracting features disclosed in at least one of U.S. patent applicationSer. Nos. 11/244,473, 10/744,276, 10/511,983, 09/833,397, 09/669,932,11/277,865, and U.S. Pat. Nos. 5,594,830, 5,237,341, 6,447,135,6,347,873, 6,099,135, and 7,192,174, the contents of each areincorporated by reference herein.

Volumetric Light-Scattering Region or Element

In one embodiment of this invention, the light emitting device comprisesone or more volumetric light scattering regions, layers or elementscomprising dispersed phase domains or voids. The matrix or dispersedphase domains may be a gaseous material (hollow lightguide or voideddiffuser, respectively, for example) or a light transmitting material.The volumetric or surface relief light scattering regions of one or moreembodiments of this invention may scatter light isotropically oranisotropically. In one embodiment of this invention, a lightguidecomprises a diffusing film comprising dispersed phase domains within apolymer matrix. Processing and choice of materials can createnon-spherical domains which will scatter light anisotropically. Othermethods for creating volumetric diffusing elements or diffusersincluding symmetric and asymmetric shaped domains are described in U.S.Pat. Nos. 5,932,342, 6,346,311, 6,940,643, 6,673,275 6,567,215 and6,917,396, the contents of each are incorporated by reference herein.Multi-region diffusers may also be used such as those disclosed in U.S.patent application Ser. No. 11/197,246, the contents are incorporated byreference herein.

Haze is one method for measuring the amount of wide angle scattering inan element. In one embodiment of this invention, the haze of the of thevolumetric light scattering element, surface relief light scatteringelement, light scattering lens, or light redirecting element measuredaccording to ASTM D1003 with a BYK Gardner Hazemeter is at least one of5%, 10%, 20%, 50%, 80%, 90%, or 99%.

Clarity is method for measuring the narrow angle scattering of a lightscattering element. In one embodiment of this invention, the clarity ofthe of the volumetric light scattering element, surface relief lightscattering element, light scattering lens, or light redirecting elementmeasured with a BYK Gardner Hazemeter is less than one of 5%, 10%, 20%,50%, 80%, 90%, or 99%.

The total luminous transmittance in the 0/d geometry of a lightscattering element or light transmitting material is one method formeasuring the forward scattering efficiency in an element. In oneembodiment of this invention, the transmittance of the of the volumetriclight scattering element, surface relief light scattering element, lightscattering lens, or light redirecting element measured according to ASTMD1003 with a BYK Gardner Hazemeter is at least one of 5%, 10%, 20%, 50%,80%, 90%, or 99%.

One or more of the diffusing (scattering) regions may have an asymmetricor symmetric diffusion profile in the forward (transmission) or backward(reflection) directions. In one embodiment of this invention, the lightemitting device comprises more than one volumetric light scatteringregion. The scattering regions or layers may be optically coupled orseparated by another material or an air gap. In one embodiment of thisinvention, the volumetric light scattering regions have a separationdistance greater than 5 microns and less than 300 mm. In one embodimentof this invention, a rigid, substantially transparent material separatestwo diffusing regions. In another embodiment of this invention, theasymmetrically diffusive regions are aligned such that the luminanceuniformity of a light emitting device is improved. In anotherembodiment, the spatial luminance profile of a light emitting deviceusing a linear or grid array of light sources is made substantiallyuniform through the use of one or more asymmetrically diffusing regions.

The use of a volumetric anisotropic light scattering element or regionin the light emitting device allows the scattering region to beoptically coupled to the light guide such that it will still supportwaveguide conditions for a first portion of light. An anisotropicsurface relief scattering region on the surface of the light guide or asurface of a component optically coupled to the light guide willsubstantially scatter light in that region out of the light guide, thusnot permitting spatially uniform out-coupling in the case of scatteringover a significant portion of the light guide surface.

In one embodiment of this invention, a light emitting device comprises alightguide with an anisotropic light scattering region whereinasymmetrically shaped dispersed phase domains of one polymer withinanother matrix polymer contribute to the anisotropic light scattering.The anisotropic scattering region may be non-polarization dependentanisotropic light scattering (NPDALS) or polarization dependentanisotropic light scattering (PDALS). Light fixtures with polarizedlight output can reduce the glare off of surfaces and are discussed inU.S. Pat. No. 6,297,906, the contents of which are incorporated hereinby reference.

The amount of diffusion in the x-z and y-z planes for the NPDALS orPDALS regions affects the luminance uniformity and the angular lightoutput profiles of the light emitting device. By increasing the amountof diffusion in one plane preferentially over that in the other plane,the angular light output from the light emitting device isasymmetrically increased. For example, with more diffusion in the x-zplane than the y-z plane, the angular light output (measured in the FWHMof the intensity profile) is increased in the x-z plane. The diffusionasymmetry introduced through one or more of the anisotropiclight-scattering regions or the light filtering directional controlelement can allow for greater control over the viewing angle, colorshift, color uniformity, luminance uniformity, and angular intensityprofile of the light emitting device and the optical efficiency of thelight emitting device. In another embodiment, the amount of diffusion(measured as FWHM of the angular intensity profile) varies in the planeof the diffusing layer. In another embodiment, the amount of diffusionvaries in the plane perpendicular to the plane of the layer (zdirection). In another embodiment of this invention, the amount ofdiffusion is higher in the regions in close proximity of one or more ofthe light sources.

The birefringence of one or more of the substrates, elements ordispersed phase domains may be greater than 0.1 such that a significantamount of polarization selectivity occurs due to the difference in thecritical angle for different polarization states when this opticallyanisotropic material is optically coupled to or forms part of the lightguide. An example of this polarization selectivity is found in U.S. Pat.No. 6,795,244, the contents are incorporated herein by reference.

Alignment of Major Diffusing Axis in Anisotropic Light Scattering Region

The alignment of the major axis of diffusion in one or more of theanisotropic light-scattering regions may be aligned parallel,perpendicular or at an angle θ₃ with respect to the optical axis of alight source or edge of the lightguide. In one embodiment, the axis ofstronger diffusion is aligned perpendicular to the length of a linearlight source in a cold-cathode fluorescent edge-lit light emittingdevice. In another embodiment of this invention, the axis of strongerdiffusion is aligned perpendicular to the length of a linear array ofLEDs illuminating the edge of lightguide in an edge-lit light emittingdevice.

Domain Shape

The domains within one or more light scattering regions may be fibrous,spheroidal, cylindrical, spherical, other non-symmetric shape, or acombination of one or more of these shapes. The shape of the domains maybe engineered such that substantially more diffusion occurs in the x-zplane than that in the y-z plane. The shape of the domains or domainsmay vary spatially along one or more of the x, y, or z directions. Thevariation may be regular, semi-random, or random.

Domain Alignment

The domains within a diffusing layer may be aligned at an angle normal,parallel, or an angle θ₄ with respect to an edge of the diffusing layeror a linear light source or array of light sources, light source opticalaxis, light emitting device optical axis, or an edge of the lightguideor light redirecting optical element. In one embodiment, the domains ina diffusing region are substantially aligned along one axis that isparallel to a linear array of light sources. In another embodiment ofthis invention, the alignment of the dispersed phase domains rotatesfrom a first direction to a second direction within the region. In oneembodiment of this invention, the light emitting device comprises avolumetric light scattering region wherein the domains are alignedsubstantially parallel to one or more of the x direction, y direction, zdirection, or an angle relative to the x, y, or z direction. In anotherembodiment of this invention, the major dimension of the domains arealigned by rotating an element or component of the device to provideadjustable light output profiles.

Domain Location

The domains may be contained within the volume of a continuous-phasematerial or they may be protruding (or directly beneath a partiallyconformable protrusion) from the surface of the continuous-phasematerial.

Domain Concentration

The domains described herein in one or more light-diffusing regions maybe in a low or high concentration. When the diffusion layer is thick, alower concentration of domains is needed for an equivalent amount ofdiffusion. When the light-diffusing layer is thin, a higherconcentration of domains or a greater difference in refractive index isneeded for a high amount of scattering. The concentration of thedispersed domains may be from less than 1% by weight to 50% by weight.In certain conditions, a concentration of domains higher than 50% byvolume may be achieved by careful selection of materials andmanufacturing techniques. A higher concentration permits a thinnerdiffusive layer and as a result, a thinner light emitting device orlight filtering directional control element. The concentration may alsovary spatially along one or more of the x, y, or z directions. Thevariation may be regular, semi-random, or random.

Index of Refraction

The difference in refractive index between the domains and the matrix inone or more of the NPDALS, PDALS or other light scattering regions maybe very small or large in one or more of the x, y, or z directions. Ifthe refractive index difference is small, then a higher concentration ofdomains may be required to achieve sufficient diffusion in one or moredirections. If the refractive index difference is large, then fewerdomains (lower concentration) are typically required to achievesufficient diffusion and luminance uniformity. The difference inrefractive index between the domains and the matrix may be zero orlarger than zero in one or more of the x, y, or z directions. In oneembodiment of this invention, the refractive index of the domains isn_(px), n_(py), n_(pz) and in the x, y, and z directions, respectivelyand the refractive index of the matrix or continuous phase region isn_(mx), n_(my), n_(mz) in the x, y, and z directions, respectively,wherein at least one of |n_(px)−n_(mx)|>0.001, |n_(py)−n_(my)|>0.001, or|n_(px)−n_(mx)|>0.001.

The refractive index of the individual polymeric domains is one factorthat contributes to the degree of light scattering by the film.Combinations of low- and high-refractive-index materials result inlarger diffusion angles. In cases where birefringent materials are used,the refractive indexes in the x, y, and z directions can each affect theamount of diffusion or reflection in the processed material. In someapplications, one may use specific polymers for specific qualities suchas thermal, mechanical, or low-cost; however, the refractive indexdifference between the materials (in the x, y, or z directions, or somecombination thereof) may not be suitable to generate the desired amountof diffusion or other optical characteristic such as reflection. Inthese cases, it is known in the field to use small domains, typicallyless than 100 nm in size to increase or decrease the average bulkrefractive index. Preferably, light does not directly scatter from theseadded domains, and the addition of these domains does not substantiallyincrease the absorption or backscatter.

During production of the light filtering directional control element orone of its regions, the refractive index of the domains or the matrix orboth may change along one or more axes due to crystallization, stress-or strain-induced birefringence or other molecular or polymer-chainalignment technique.

Additive materials can increase or decrease the average refractive indexbased on the amount of the materials and the refractive index of thepolymer to which they are added, and the effective refractive index ofthe material. Such additives can include: aerogels, sol-gel materials,silica, kaolin, alumina, fine domains of MgF2 (its index of refractionis 1.38), SiO2 (its index of refraction is 1.46), AlF3 (its index ofrefraction is 1.33-1.39), CaF2 (its index of refraction is 1.44), LiF(its index of refraction is 1.36-1.37), NaF (its index of refraction is1.32-1.34) and ThF4 (its index of refraction is 1.45-1.5) or the likecan be considered, as discussed in U.S. Pat. No. 6,773,801, the contentsincorporated herein by reference. Alternatively, fine domains having ahigh index of refraction, may be used such as fine particles of titania(TiO2) or zirconia (ZrO2) or other metal oxides.

Other modifications and methods of manufacturing anisotropic lightscattering regions, and light emitting devices and configurationsincorporating anisotropic light scattering elements are disclosed inU.S. Pat. No. 7,278,775, the contents of which are incorporated byreference herein. The modifications and configurations disclosed thereinmay be employed in an embodiment of this invention to create a visuallyuniform (greater than 70% luminance uniformity) light output surface, adesired angular luminous intensity profile, or an efficient (opticalefficiency greater than 70%) light emitting device comprising a lightfiltering directional control element.

Scattering Element or Region Location

The light emitting device of an embodiment of this invention comprisesone or more isotropic, anisotropic, volumetric or surface relief lightscattering elements or regions. In one embodiment of this invention, thelight scattering or extraction region is patterned or graded indiffusion. One or more of the regions or elements may be located as aseparate element or layer, coupled to a lens, cover, or housing, withinthe lenticular lens structure, within the lenticular lens substrate,within the light absorbing region, within the light reflecting region,within the light transmitting region, within or adhered to thelightguide or a component of the lightguide, within or coupled to alight redirecting element, between the light filtering directionalcontrol element and the light emitting device light output surface,between the light filtering directional control element and thelightguide or between the lightguide and one or more light emittingsources such as LED's. The light scattering region may be opticallycoupled to one or more elements of the light filtering directionalcontrol element or one or more elements of the light emitting device. Inone embodiment of this invention, the light scattering element isoptically coupled to one or more components of the light filteringdirectional control element or the light emitting device using a lowrefractive index adhesive. In a further embodiment of this invention, alight filtering directional control element comprises a light scatteringfilm optically coupled using a pressure sensitive adhesive to the apexregion of the lenticules such that the anisotropic light scattering filmprovides a substantially planar output surface that is more resistant toscratches. In one embodiment, the loss of the refractive power at theapex of the lenticules where the pressure sensitive adhesive effectivelyindex matches out the interface increases the FWHM angular intensityoutput in a plane perpendicular to the lenticules by less than oneselected from the group of 2 degrees, 5 degrees, 10 degrees, or 20degrees relative to the light scattering film separated from thelenticular lens array by an air gap. In a further embodiment of thisinvention, the light scattering element, such as the volumetric lightscattering region, is located in at least one of within the lightguide,within a substrate, within a multi-region diffuser, between thereflective element and the lightguide, within a coating on a lightguide,within a film optically coupled to the lightguide, within an adhesivebetween two elements of a light emitting device.

Light Scattering Region or Element Diffusion Angles

In one embodiment of this invention, the light scattering elementchanges the angular direction of a significant portion of the incidentlight upon transmission through the element. In one embodiment of thisinvention, the angular full-width at half maximum intensity of lighttransmitted through a light scattering element or region from collimatedlaser light from a 532 nanometer laser diode is greater than oneselected from the group of 5 degrees, 10 degrees, 20 degrees, 30degrees, 40 degrees, 50 degrees, and 60 degrees in a first output planenormal to the output surface. In a further embodiment of this invention,the angular full-width at half maximum intensity of light transmittedthrough a light scattering region or element from collimated laser lightfrom a 532 nanometer laser diode is greater than one selected from thegroup of 5 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50degrees, and 60 degrees in a second output plane normal to the outputsurface and first output plane. In one embodiment of this invention, theangular FWHM intensity of the transmitted light in the first outputplane is substantially equal to the angular FWHM intensity of the lightin the second output plane. In another embodiment of this invention, thedifference between the angular FWHM intensity of the transmitted lightin the first output plane and second output plane is less than oneselected from the group of 1 degrees, 2 degrees, 5 degrees, 10 degrees,and 15 degrees when averaged over the light emitting surface.

Volumetric Scattering Region Pattern

In one embodiment of this invention, the volumetric scattering region orsurface relief structure is patterned or graded in diffusion. Thepattern may vary in within a linear direction, across a two-dimensionalplane, or within a three-dimensional volume. For example, the volumetricscattering region could be a substantially planar volumetric scatteringregion comprising light scattering dispersed phase domains with raisedlinear ribs that also comprises light scattering dispersed phasedomains. In another embodiment of this invention, the volumetricscattering region is substantially planar, but is only optically coupledto a second element, such as a non-scattering region, in atwo-dimensional spatial pattern. In this embodiment, light within aspecific angular range may optically couple into the regions where thevolumetric scattering region is optically coupled to the non-scatteringregion and a portion of the light may totally internally reflect inregions where the volumetric scattering region is not optically coupledto the non-scattering region. In another embodiment of this invention,volumetric scattering lightguide comprises a volumetric light scatteringregion with a dimension that varies in at least one of the x, y, and zdirections. The pattern or variation may include a regular array offeatures or those that vary in size, shape or distance in at least onedirection. The pattern could have a element of randomization (such arandom deviation of shape, size, separation, or other feature) orpartial randomization. Examples of patterned or graded diffusers andtheir patterns are disclosed in U.S. patent application Ser. Nos.11/949,222, 10/984,407, 10/984,390 and U.S. Pat. No. 6,867,927, thecontents of each are incorporated by reference herein.

In another embodiment of this invention, a volumetric scatteringlightguide comprises a volumetric scattering region physically coupledto a non-scattering region wherein at least one of a low refractiveindex region and air gap region is disposed in a region between thevolumetric light scattering region and a non-scattering region of thevolumetric scattering lightguide. In one embodiment of this invention, apattern of comprising low refractive index regions comprising lowrefractive index materials is disposed in regions between the volumetricscattering region. In a further embodiment, low refractive index regionsand air void regions are disposed between the volumetric scatteringregion and non-scattering region in a volumetric scattering lightguide.

Low Refractive Index Region

In one embodiment of this invention, a lightguide comprises a lowrefractive index region disposed in the optical path between a lightsource and a light output surface of the lightguide. In a furtherembodiment of this invention, a volumetric scattering lightguidecomprises a non-scattering region, a volumetric scattering region, and alow refractive index disposed between the non-scattering region and thevolumetric scattering region. In one embodiment of this invention, a lowrefractive index region comprises a material wherein the ratio of therefractive index of the low refractive index region to the refractiveindex of the non-scattering region of a lightguide optically coupled tothe low refractive index region is less than 0.98 when measured at thesodium wavelength (589 nm). In another embodiment of this invention, alow refractive index region comprises a material wherein the refractiveindex of the low refractive index material is at least 0.03 less thanthe refractive index of the non-scattering region of a lightguideoptically coupled to the low refractive index region when measured atthe sodium wavelength (589 nm). In a further embodiment of thisinvention, a low refractive index region comprises a material whereinthe refractive index of the low refractive index region is less than oneselected from the group of 1.58, 1.51, 1.46, 1.43, 1.41, 1.40, 1.38,1.34, and 1.30 when measured at the sodium wavelength (589 nm).

In another embodiment of this invention, a volumetric scatteringlightguide comprises a low refractive index region disposed to andoptically coupled between a non-scattering region and a volumetricscattering region and the low refractive index region comprises amaterial with a refractive index lower than the non-scattering regionand lower than the matrix material in the volumetric scattering region.In this embodiment, the low refractive index region is disposedin-between the non-scattering region and the volumetric scatteringregion and its low refractive index filters high angle light andprevents it from entering into the volumetric light scattering regiondirectly. In one embodiment of this invention, a low refractive indexregion comprises a material wherein the ratio of the refractive index ofthe low refractive index region to the refractive index of the matrix ofthe volumetric scattering region in a volumetric scattering lightguideoptically coupled to the low refractive index region is less than 0.98when measured at the sodium wavelength (589 nm). In another embodimentof this invention, a low refractive index region comprises a materialwherein the refractive index of the low refractive index region is atleast 0.03 less than the refractive index of the matrix region of avolumetric scattering region of a volumetric scattering lightguideoptically coupled to the low refractive index region when measured atthe sodium wavelength (589 nm).

The low refractive index region comprises a light transmitting materialand may further comprises dispersed phase domains, voids, or otherelements. In one embodiment of this invention, a volumetric scatteringlightguide comprises a volumetric scattering region with a matrixmaterial optically coupled to a non-scattering region wherein the matrixmaterial of the volumetric scattering region is a low refractive indexregion with a refractive index lower than the refractive index of thenon-scattering region to which it is optically coupled.

The low refractive index region may be conformal in shape to a secondregion, such as a non-scattering region, so that at least one portion ofthe low refractive index region conforms in shape to a non-planarsurface relief pattern on the surface to which it is optically coupled.In one embodiment of this invention, the low refractive index regioncomprises at least one of an aerogel, a sol-gel, a thermoplasticpolymer, a thermoset polymer, a fluoropolymer, a polymer with voidscomprising a gas, a fluorinated adhesive, and other adhesives. In oneembodiment of this invention, the low refractive index region isoptically coupled to the lightguide and physically couples a lightguidecomprising a non-scattering region to at least one of a volumetricscattering region or element, a light redirecting element, a collimationfilm, a protective film, a lens, a covering, or housing.

In one embodiment of this invention, the low refractive index region isdisposed on a lightguide comprising a non-scattering region by at leastone method selected from the group of coating (wet or dry processes, dipcoating, extrusion coating, roll coating, brush coating, spray coating,UV cured coating, powder coating, deposition coating, sol gel coating,epitaxy coating, air knife coating, anilox coating, curtain coating,flexo coating, gap coating, gravure coating, micro-gravure coating, hotmelt coating, knife-over-roll coating, metering rod coating, Myer barcoating, roller coating, rotary screen coating, silk screen coating,slot tie coating, extrusion coating, conformal coating, vacuumdeposition coating, CVD coating, PVD coating, and other coating methodsknown in the printing and polymer coating industries), adhesion,co-extruded layer, physical coupling by employing a tie layer oradhesion promoting surfaces or layer, injection molding, or other formsuitable for providing a low refractive index material as discussedherein, in the patent applications referenced herein, and known in theindustry.

Low Refractive Index Pattern

The low refractive index region may be comprised of smaller regions of alow refractive index material in a pattern or arrangement. The lowrefractive index region pattern may be a substantially planar region orit may comprise a regular, irregular, random, or quasi-random surface orvolumetric features. In one embodiment of this invention, the lowrefractive index region is disposed between more than one non-scatteringregion, between more than one volumetric or surface relief scatteringregion, or between two of the same or dissimilar regions or elementsselected from the group of non-scattering region, volumetric scatteringregion, surface relief region, light extracting region, reflectiveelement, light redirecting element, light source, housing, lens,volumetric diffuser, surface relief diffuser, optical film.

In one embodiment of this invention, the pattern of low refractive indexregions enables the selective control of light flux entering into thevolumetric scattering region due to the angular filtering caused by theshift in the critical angle relative to the volumetric scattering filmbeing directly coupled to the non-scattering region directly. In thisembodiment, the light traveling at angles higher than the critical angleat the interface between the low refractive index region and thenon-scattering region will reflect back into non-scattering region. Inthis embodiment, the regions where the low refractive index is coupledto the non-scattering region, less light will travel through the lowrefractive index toward the volumetric scattering region. In oneembodiment of this invention, a volumetric scattering lightguidecomprises a non-scattering region and a volumetric scattering regionthat is optically coupled to the non-scattering region directly, throughan intermediate low refractive index region, and through an air gapregion. In this embodiment, for a given flux of light uniformly spreadover a range of angles from 0 degrees to 90 degrees to the interface, ahigh amount of light flux within the non-scattering region will becoupled into the volumetric scattering region in the areas that aredirectly, optically coupled to the non-scattering region, a mediumamount of flux will be coupled into the volumetric scattering region bytraveling through the low refractive index region, and a low amount offlux will be coupled into the volumetric scattering region by travelingthrough the air gap region.

Low Refractive Index Region Angular Filtering

In one embodiment of this invention, a volumetric scattering lightguidecomprises a low refractive index region disposed to and opticallycoupled between a non-scattering region and a volumetric scatteringregion and the low refractive index region comprises a material with arefractive index lower than the non-scattering region. In thisembodiment, the light at high incident angles that would normally coupleinto a volumetric light scattering region optically coupled directly toa non-scattering region is reflected, thus filtered from directlycoupling into the volumetric light scattering region. In a furtherembodiment of this invention, a volumetric scattering lightguidecomprises a low refractive index region disposed to and opticallycoupled between a non-scattering region and a volumetric scatteringregion and the low refractive index region comprises a material with arefractive index lower than the non-scattering region and matrixmaterial of the volumetric scattering region. In this embodiment, thelight traveling at angles higher than the critical angle at theinterface between the low refractive index region and the non-scatteringregion will reflect back into non-scattering region. In one embodimentof this invention, the light extracting region does not directly receivelight from a light source disposed at a first input surface after it istransmitted into a first non-scattering region through the first inputsurface. In this embodiment, the light is not received by the lightextraction region unless it has reflected off of a surface after beingemitted from a light source.

In one embodiment, a volumetric scattering lightguide is illuminatedfrom the edge and the volumetric scattering lightguide is disposed adistance, D, from the edge of the lightguide as shown in FIG. 27. Inthis embodiment, light from the light source is refracted upon enteringthe non-scattering region of the volumetric scattering lightguide, andthis light travels through the non-scattering region. Furthermore, inthis embodiment, the direct light from the light source (that which hasnot totally internally reflected) that is incident upon the interfacebetween the non-scattering region and the low refractive index region atangles above the critical angle and will totally internally reflect atthe interface and not cause undesirable regions of high luminance on thelight emitting surface of the volumetric scattering lightguide of thelight emitting device.

In one embodiment of this invention, the low refractive index regionenables the use of a stronger diffuser or volumetric scattering region(higher full angular width at half maximum intensity), because there isless light from the light source directly illuminating the volumetricscattering region the diffuser which would cause a region of highluminance and low luminance micro-uniformity and/or luminancemacro-uniformity. In one embodiment of this invention, a lightguidecomprises a low refractive index region disposed between lightextracting region and a non-scattering region and the luminancemacro-uniformity or luminance micro-uniformity of at least one outputsurface is greater than one selected from the group of 50%, 60%, 70%,80%, 90% and 95%.

Furthermore, the use of a stronger diffuser in a volumetric scatteringlightguide can improve the output coupling efficiency of the lightguideand further increase the optical efficiency of the light emittingdevice. In one embodiment of this invention, the optical efficiency ofthe volumetric scattering lightguide or light emitting device comprisingthe same is greater than one selected from the group of 50%, 60%, 70%,80%, 90% and 95%.

The following equations in this section related to critical angles,light angles, refractive index and distances are presented in thecontext of the embodiment illustrated in FIG. 27. In one embodiment ofthis invention, the distance, D, between an input edge and thevolumetric scattering region, the thickness, t, of the non-scatteringregion of the lightguide and the length, L, of the non-scattering regionof the lightguide, L, are designed such that the low refractive indexregion prevents light from a light source disposed at the input edgereaching the volumetric scattering region directly. In the embodimentillustrated in FIG. 27, the smallest angle of light (measured from thenormal to the interface between the non-scattering region and the lowrefractive index region) from the input edge within the non-scatteringregion of the volumetric scattering lightguide which would reach the lowrefractive index region directly is shown trigonometrically as:

$\theta_{s} = {{\tan^{- 1}\left( \frac{D}{t} \right)}.}$

By using a low refractive index region, one can design volumetricscattering lightguide such that there is no direct illumination (lightreaching without reflecting) of the volumetric scattering region byusing a low refractive index region where the critical angle for lightat the interface between the non-scattering region and the lowrefractive index region is less than lowest angle of light from theinput edge that would reach the volumetric scattering region directly.Thus, one can use a material for the low refractive index region with arefractive index such that

θ_(c)<θ_(s) where θ_(c) is the critical angle for the interface definedby

$\theta_{c} = {\sin^{- 1}\left( \frac{n_{l}}{n_{ns}} \right)}$where n_(l) is the refractive index of the material in the lowrefractive index region and the n_(ns) is the refractive index of thematerial of the non-scattering region. Rewriting in this, one can definea maximum for the low refractive index region, n_(l(max)) as

$n_{l{(\max)}} < {n_{ns} \times {{\sin\left( {\tan^{- 1}\left( \frac{D}{t} \right)} \right)}.}}$Thus, n_(l(max)) is the maximum value for the low refractive indexregion in this embodiment to prevent light from directly reaching thevolumetric light scattering region (or other type of light extractingregion).

This may also be written to determine a safe distance, D_(min), (closestone can place the volumetric scattering region or light extractingregion to the input edge of the non-scattering region) to position thevolumetric scattering region so as to not receive direct light as

$D_{\min} > {t \times {\tan\left\lbrack {\sin^{- 1}\left( \frac{n_{l}}{n_{ns}} \right)} \right\rbrack}}$

In one embodiment of this invention, a volumetric scattering lightguidecomprises a non-scattering region, a light extracting region, and a lowrefractive index region such that the refractive index of the lowrefractive index region is less than n_(l(max)). In a further embodimentof this invention, a volumetric scattering lightguide comprises anon-scattering region, a volumetric scattering region, and a lowrefractive index region wherein the volumetric scattering region ispositioned at a distance, D, from a first input edge of thenon-scattering region of the volumetric scattering lightguide whereD>D_(min).

Light Reflecting Element and Region

In one embodiment of this invention, a light emitting device comprises alight reflecting element. In one embodiment of this invention, a lightreflecting element comprises a light reflecting region. The lightreflecting region may be specularly reflecting, diffusely reflecting orsome combination in-between. The light reflecting region may comprise areflective ink, beads or other additives that substantially reflectlight of one or more wavelength ranges. The light reflecting region maytransmit a portion of incident light. In one embodiment of thisinvention, the light reflecting region is a low light transmittingregion and has luminous transmittance measured according to ASTM D1003less than one selected from the group of 5%, 10%, 15%, 20%, 30%, and50%. In another embodiment of this invention, the low light transmittingregion is a light reflecting region and has a diffuse reflectancemeasured in the d/8 geometry with the specular component included ofgreater than one selected from the group of 60%, 70%, 80%, 90%, and 95%.

The reflective additive used in an ink or polymer system may includeBaSO4, TiO2, organic clays, fluoropolymers, glass beads, silicone beads,cross-linked acrylic or polystyrene beads, alumina, or other materialsknown in the diffusion screen or film industry for backlights orprojection screens such that the refractive index difference betweenthem and a supporting polymer matrix or binder is sufficiently high toreflect light a significant portion of incident light (such as greaterthan 80% diffuse reflectance). The light reflecting region may also be alight reflecting material such as PTFE, or it may comprise a blend ofthermoplastic polymers such as described in U.S. patent application Ser.No. 11/426,198, or U.S. Pat. Nos. 5,932,342, 5,825,543, and 5,268,225,the text of each is incorporated by reference herein where therefractive index between the two polymers is chosen to be very high suchthat the light reflects from the film. In another embodiment of thisinvention, the light reflecting region is a voided film such thosedescribed in U.S. Pat. Nos. 7,273,640, 5,843,578, 5,275,854, 5,672,409,6,228,313, 6,004,664, 5,141,685, and 6,130,278, and U.S. patentapplication Ser. No. 10/020,404, the contents of each are incorporatedby reference herein.

The light reflecting region may comprise nanoparticle dispersions suchas nanodispersions of aluminum or silver or other metals that can createa specularly reflecting ink. In one embodiment of this invention, alight emitting device comprises a specular light reflecting region whichrecycles the incident light from within the light emitting device toprovide uniformity and the light output from the device is substantiallycollimated from a light redirecting element.

In one embodiment of this invention, the light reflecting region is amultilayer dielectric coating or a multilayer polymeric reflector filmsuch as described in U.S. Pat. Nos. 7,038,745, 6,117,530, 6,829,071,5,825,543, and 5,867,316, the contents of each are incorporated byreference herein, or DBEF film produced by 3M. A multilayer polymericreflective film can have a reflectance in the visible spectrum greaterthan 94% and thus can be more efficient in an optical system. Themulti-layer polymeric reflector film may be specularly reflective,diffusely reflective, diffusely transmissive, anisotropically forwardscattering or anisotropically backward scattering for one or morepolarization states. In a light emitting device where the lightreflecting regions are a multi-layer polymeric reflector, the low lightloss enables more reflections before the light is absorbed and thus acavity within the light emitting device can be made thinner and/or thelight transmitting apertures can be smaller, thus providing higheruniformity and more light filtering in a thinner form factor.

In one embodiment of this invention, the light reflecting element is asymmetrically diffusely reflecting white reflecting film such voided PETfilms with our without additives such as titanium dioxide or bariumsulfate. A specularly reflecting film may also be used such asmetallized aluminized PET film or ESR multilayer reflective film from 3MCompany or DBEF reflective polarizer film from 3M Company. Lightreflecting elements can be composed of light transmitting materials. Inanother embodiment of this invention, light emitting device comprises avolumetric asymmetrically reflecting element. The asymmetricallyreflecting element may be an anisotropically backscattering volumetricdiffuser, a volumetric forward asymmetrically scattering diffuseroptically coupled to a specular reflector or other volumetric or surfacerelief elements that reflect light anisotropically. In anotherembodiment of this invention, the reflector may be a metal such asaluminum or a metallic compound. The light reflecting element may be asheet or other component or portion of the housing that is comprised ofa light reflecting component or a metal or metallic layer or otherreflecting component such as a polished aluminum housing. The lightreflecting region may also be a brushed (or otherwise imparted withsubstantially linear features) aluminium or a brushed, embossed coatingsuch that the element reflects anisotropically. In one embodiment ofthis invention, a light emitting device comprises a light reflectingelement with a d/8 diffuse reflectance greater than one selected from70%, 80%, 90%, or 95%. In a further embodiment of this invention, alight emitting device comprises an anisotropic light reflecting elementwith a d/8 diffuse reflectance greater than one selected from 70%, 80%,90%, or 95%. In one embodiment of this invention, a light emittingdevice comprises a light reflecting film disclosed in at least one ofU.S. Pat. Nos. 4,377,616, 4,767,675, 5,188,777, 6,497,946, 6,177,153,and U.S. patent application Ser. No. 10/020,404, the contents of eachare incorporated by reference herein.

Diffusely Reflecting Optical Element

In one embodiment of this invention, the light reflecting element is adiffusely reflecting optical element. A diffusely reflecting element isone wherein a significant portion of the incident light changes angulardirection upon reflecting from the element. In one embodiment of thisinvention, the angular full-width at half maximum intensity of lightreflected from a diffusely reflecting element from a collimated laserlight from a 532 nm laser diode is greater than 2 degrees in at leastone plane of reflection. If a reflecting element is optically coupled toa lightguide, a diffusely reflecting element will typically couple morelight out of the lightguide than a specularly reflecting opticalelement. The design of the amount of diffusion or angular spread (FWHM)of light reflected from a diffusely reflecting element can be chosen tobalance uniformity of the light emitting surface and the opticalextraction efficiency. In one embodiment of this invention, the lightreflecting element is not optically coupled to the volumetric scatteringlightguide. In other embodiment of this invention, a diffuselyreflecting optical element is optically coupled to the volumetricscattering lightguide.

Specularly Reflecting Optical Element

In other embodiment of this invention, a specularly reflecting opticalelement is optically coupled to the volumetric scattering lightguide. Aspecularly reflecting element is one wherein only a very small portionof the incident light changes angular direction upon reflecting from theelement. In one embodiment of this invention, the angular full-width athalf maximum intensity of light reflected from a specular reflectingelement from a collimated laser light from a 532 nm laser diode is lessthan 2 degrees in at least one plane of reflection. If a reflectingelement is optically coupled to a lightguide, a specularly reflectingelement will typically couple less light out of the lightguide than adiffusely reflecting optical element. The design of the amount ofdiffusion or angular spread (FWHM) of light reflected from a specularlyreflecting element can be chosen to balance uniformity of the lightemitting surface and the optical extraction efficiency. In oneembodiment of this invention, a specularly reflecting optical element isoptically coupled to the volumetric scattering lightguide.

Reflector

In one embodiment of this invention, a light emitting device comprises areflector disposed to receive direct and indirect light from a lightsource which does not satisfy the total internal reflection condition.In one embodiment of this invention, the reflector is a light reflectingelement which reflects or reflects and absorbs substantially all of theincident light from a light source. An example of a reflector used in alight emitting device can include a bezel or frame on a lightguide. Thelight source may be disposed substantially within the reflector and thereflector may extend out over a portion of one or both faces or surfacesof a lightguide. The reflector may be a metal such as aluminum oraluminum composite and may be thermally coupled to the thermal transferelement. In one embodiment of this invention, the reflector is at leastone thermal transfer element in the light emitting device system.Reflectors can also be composed of light transmitting materials.

Optical Axis of the Light Emitting Device

For light emitting devices with luminous intensity output profiles thatare substantially symmetric about a first angular direction, the opticalaxis of the light emitting device is the first angular direction. In thecase of light emitting devices with luminous intensity output profilesthat not are not substantially symmetric about a first angulardirection, the optical axis of the light emitting device is the angle orangular range of peak luminous intensity. Similarly, for light emittingdevices in applications where the emitted light is designed to compriselight in the non-visible portion of the electromagnetic spectrum, theoptical axis of the light emitting device is the first angular directionof symmetry of the radiant intensity or angle or angular range of peakradiant intensity for symmetric and asymmetric light output profiles,respectively.

In cases where the luminescent intensity output profile is symmetric ina first output plane and asymmetric in a second plane orthogonal to thefirst, the optical axis of the light emitting device is the centralangle of symmetry in the first plane and the angle of peak luminousintensity in the second plane. For downlights, troffers, pendants,backlights and many other light fixture light emitting devices, theoptical axis is typically normal to the output surface or mountingelement and in a vertical direction. For wall-washing applications,however, the optical axis of the light emitting device may be at anangle relative to the housing, mounting or other component such aslightguide. In one embodiment of this invention, the optical axis of thelight emitting device is aligned parallel, perpendicular, or at anangle, θ1, with respect to at least one of the optical axis of at leastone light source, the normal to the light output surface or first orsecond light output region, the output plane, the edge or surface of anelement (optical element or otherwise such as a mechanical mount orhousing surface) of the light emitting device, or the edge or surface ofan object of illumination such as a desk, hallway floor, wall, orwindow. In one embodiment of this invention, the angle θ1 is in a rangeselected from the group: greater than 10 degrees; greater than 45degrees; greater than 80 degrees; greater than 90 degrees; greater than130 degrees; 0 degrees to 5 degrees; 10 degrees to 30 degrees; 30degrees to 45 degrees; 45 degrees to 60 degrees; 60 degrees to 90degrees; and 90 degrees to 170 degrees.

Thermal Transfer Element

In one embodiment of this invention, a light emitting device comprises athermal transfer element selected from the group heat sink, heat pipe,forced air based cooling system, liquid based cooling system, activecooling systems, passive cooling systems, forced air systems,thermoelectric cooler, phase change cooler, and synthetic jet systemsuch as sold by Nuventix. In another embodiment of this invention, thethermal transfer element extends farther in a first direction which isin a first plane than a largest dimension of the upper housing of thelight emitting device in any plane which is parallel to the first plane.In another embodiment of this invention, the thermal transfer elementextends farther than a portion of the light emitting surface of thelightguide or light emitting surface of the light emitting device in thesame direction as the optical axis of the light emitting device. Otherthermal transfer elements or cooling systems may be used such as thoseused for light fixtures or light emitting devices such as disclosed inU.S. patent application Ser. Nos. 12/116,348 and 12/154,691, and U.S.Pat. No. 7,095,110, the contents of each are incorporated by referenceherein. In one embodiment of this invention, the thermal transferelement comprises a solid metal block mounting substrate such asdisclosed in U.S. Pat. No. 7,183,587, the contents of which areincorporated by reference herein. In one embodiment of this invention,the thermal transfer element has a dimension extending past the lightoutput plane in the direction of the optical axis of the light emittingdevice as shown in FIG. 22. The thermal transfer element may extend passthe light output plane and may also extend into a region disposedbetween two lightguides, between two points on the inner surface of alight transmitting material, lightguide, or light scattering lens, orbetween a first and second light output regions on a light outputsurface of a lightguide as shown in FIG. 20 a. In another embodiment,the thermal transfer element extends into a region between thelightguide and a light scattering lens. The thermal transfer element maybe an electrical component. In one embodiment of this invention, thethermal transfer element comprises one selected from the group aluminum,aluminum alloy, steel, carbon, ceramic, a metal, and an alloy. In afurther embodiment of this invention, the thermal transfer element has athermal conductivity greater than one selected from the group of 0.6W/(m·K), 1 W/(m·K), 10 W/(m·K), 100 W/(m·K), and 200 W/(m·K). Thethermal transfer element may be opaque and non-optical. A non-opticalcomponent is a component which does not perform an optical functionessential to the desired operation of the device such that if anyoptical functionality of the component were removed, the device wouldfunction in substantially the same manner optically. In one embodimentof this invention, the luminous transmittance of the thermal transferelement is less than one selected from the group of 10%, 5%, 1%, and0.5%.

Mounting Element

In one embodiment of this invention, the light emitting devicescomprises a housing. The housing can be of any desired shape, and can bemade of any desired material, a wide variety of both of which arewell-known to persons skilled in the art. Representative examples of amaterial out of which the light engine housing can be made include,among a wide variety of other materials, extruded aluminum, die castaluminum, liquid crystal polymer, polyphenylene sulfide (PPS), thermosetbulk molded compound or other composite material, any of which wouldprovide excellent heat transfer properties, which would assist indissipating heat generated by the light emitting device. In someembodiments, the light engine housing has a plurality of fin elementswhich increase the surface area of the light engine housing, therebyincreasing the heat dissipation characteristics of the light emittingdevice. In one embodiment of this invention, the mounting elementcomprises a first mounting surface such that the mounting surface issubstantially parallel to the surface to which the light emitting deviceis mounted or designed to be mounted on. In another embodiment of thisinvention, the mounting surface is substantially parallel to the circuitboard comprising at least one light source. In a further embodiment ofthis invention, the first mounting surface of the light emitting deviceis substantially planar and at an angle, ψ, to the optical axis of thelight emitting device. In one embodiment of this invention, the angle ψis in a range selected from the group: greater than 10 degrees; greaterthan 45 degrees; greater than 80 degrees; greater than 90 degrees;greater than 130 degrees; 0 degrees to 5 degrees; 10 degrees to 30degrees; 30 degrees to 45 degrees; 45 degrees to 60 degrees; 60 degreesto 90 degrees; and 90 degrees to 170 degrees. In a further embodiment ofthis invention, the mounting element includes the thermal transferelement.

Driver and Other Electronics

In one embodiment of this invention, the light emitting device comprisesdriving electronics for the light source. In one embodiment of thisinvention, the driving electronics includes at least one of anelectrical ballast, LED driver, AC-DC transformer, DC-AC transformer,DC-DC transformer, switching electronics, pulsing or modulatingelectronics, color control electronics, safety electronics, fuses,breakers, surge-protection electronics, optical sensing electronics,color based feedback electronics, sensors (optical, electrical,mechanical, thermal, pressure, motion, etc.), electrical connectors,plugs, power cords, switches, displays, liquid crystal panels anddrivers, and other electrical components known in the lighting anddisplay industry to be suitable for use in a light fixture or lightemitting device. In one embodiment of this invention, a light emittingdevice comprises an electrical component selected from U.S. Pat. Nos.6,016,038, 6,016,038, 6,528,954, 6,211,626, 7,441,934, and 7,407,307,the contents of each are incorporated by reference herein. In oneembodiment of this invention, the thermal transfer element comprises atleast of the aforementioned electrical components. The electricalcomponent may be opaque and non-optical. In one embodiment of thisinvention, the luminous transmittance of the electrical component isless than one selected from the group of 10%, 5%, 1%, and 0.5%.

In another embodiment of this invention, a light emitting devicecomprises an electrical device for controlling the color (such asindividually adjusting the output from a red, green, amber, yellow,purple, or blue LED), angular light output profile (such as by moving alens), direction of the light output profile, intensity of the lightoutput, and mode of operation (such as switching between mirror mode orlight mode).

Light Scattering Lens

In one embodiment of this invention, a light emitting device comprises alight scattering lens. A light scattering lens can be composed of lighttransmitting materials. In one embodiment of this invention, the lightscattering lens is disposed to receive light from one or morelightguides or lightguide output regions and further scatter the lightand increase luminance uniformity of the output surface. In oneembodiment of this invention, the luminance uniformity of the lightoutput surface on a light scattering lens of a light emitting device isgreater than one of 70%, 80% and 90%. The light scattering lens may alsoserve to protect the lightguides which can be sensitive to scratchingdepending on the material. The shape of the light scattering lens may beplanar, curved, quadric, hemispherical, partially spherical, spherical,polyhedral or other multifaceted, curved, or combination faceted andcurved surface. More than one light scattering lens may be used toprovide uniformity and the lenses may be co-axial or have an axialseparation distance of greater than 2 millimeters. In one embodiment,the lenses are placed with their axes separated by greater than 2 mm andthe inner lens modifies the light distribution reaching the outer lensto improve one of angular directionality, uniformity in on or moredirections, or a designed luminance from a specific viewing angle.

The light scattering lens may be surface relief, volumetric, combinationsurface relief and volumetric, absorption and re-emission scatteringtype or other light scattering type. Surface relief type diffusers andlenses may comprise surfaces with features with spatially varyingsurface normals such that the angular FWHM intensity of collimated lighttransmitted through surface is greater than 1 degree in a first outputplane. The pattern may be regular, random, substantially random,mathematically generated, optically generated (such as holographicdiffusers) etc. For purposes used herein, all surface relief patternsmay be used in an embodiment of this invention regardless of thespecifics of the individual undulations and variances of the surfacenormal. A surface relief pattern, as used herein, is considered to beindependent of how it was made and such relief surfaces include thosereferred to as holographic diffusers, light shaping diffusers,diffractive diffusers, elliptical diffusers, embossed diffusers,microlens arrays, diffractive optical elements, holographic opticalelements, prismatic arrays, pyramid arrays, arrays of cones, sandblasteddiffusers, etched diffusers, collimation films and other patterns whichdirect light into more than one direction such that the angular FWHM ofthe intensity of the output light profile is larger than the angularFWHM of the intensity of the input light profile in a first plane orsecond plane orthogonal to the first.

In one embodiment of this invention, a light emitting device comprises avolumetric light scattering lens that comprises a volumetric lightscattering region that anisotropically or isotropically scatters light.

In one embodiment of this invention, the light scattering lens comprisesa wavelength conversion material that converts a first portion of lightof a first wavelength into a second wavelength different than the first.The wavelength conversion material may be a phosphor material,down-conversion material, up-conversion material, frequency doublingmaterials, quantum dot material, nanodispersed material such asnanodispersions of gold, or other materials known to convert light ofone wavelength into another. Phosphors or other light conversionmaterials are known in the field of light emitting sources, CRT phosphormaterials, LED phosphor materials, laser photonics and other opticalfields. Lenses comprising light conversion materials include thosedisclosed in U.S. patent application Ser. Nos. 11/398,214, 10/659,240and 11/614,180, and U.S. Pat. No. 7,355,284, the contents of each areincorporated by reference herein.

In another embodiment of this invention, a light scattering lenscomprises a wavelength conversion region and a non-absorbing lightscattering region. In a further embodiment, the lens compriseswavelength conversion materials dispersed in a region comprisingnon-absorbing light scattering domains.

In one embodiment of this invention, a light emitting device comprises alight scattering lens wherein at least a portion of the inner or outersurface of the light scattering lens is a quadric surface in the formselected from one of a full or partial ellipsoid, spheroid, paraboloid,circular paraboloid, elliptic paraboloid, hyperbolic paraboloid,hyperboloid of one sheet, cone, elliptic cylinder, circular cylinder, orparabolic cylinder.

Light Redirecting Elements (LRE)

In one embodiment of this invention, a light emitting device comprises alight source, a lightguide and a light redirecting element. Lightredirecting optical elements are optical elements that direct a firstportion of incident light from a first angular direction into a secondangular direction different from the first. Light redirecting elementscan be composed of light transmitting materials. Light redirectingelements include diffusive or scattering elements, refracting elements,reflecting elements, re-emitting elements, diffractive elements,holographic elements, or a combination of two or more of theaforementioned elements. The elements may be grouped into regionsspatially or the features may be hybrid components such as arefractive-TIR fresnel lens hybrid structure. Other light redirectingelements include collimating films such as BEF film from 3M Company andbeaded bottom diffusers such as BS-700 light diffusing film from Keiwaand embossed light diffusing film UTE-22 from Wellstech Optical CompanyLtd, off-axis directing films such as IDF film from 3M company,lenticular lens arrays, microlens arrays, volumetric diffusers, surfacerelief diffusers, light filtering directional control elements, voideddiffusers, voided reflective films or materials, multi-layer reflectivefilms such as ESR from 3M, polarization reflective films such as DBEFfrom 3M, reflective polarizers, scattering polarizers and NPDALS orPDALS, lightguides, diffractive or holographic surface relief diffusersor elements, holographic volumetric diffusers or elements, microlenses,lenses, and other optical elements known in the optical industry toredirect light or a combination of two or more of the aforementionedelements or regions of elements.

The light redirecting element may be optically coupled to one or moreelement, optical elements, lightguide, or light source of the lightemitting device. In one embodiment of this invention, the lightredirecting optical element is separated by an air gap in a first regionfrom a second optical element or lightguide of the light emittingdevice. The light redirecting optical element may be optically coupledto a support substrate to position or hold in a predetermined locationwithin the light emitting device. In another embodiment of thisinvention, the light redirecting element is separated from anotheroptical element or lightguide within the device by standoff regions. Inone embodiment, the longest dimension of the standoffs in a planeperpendicular to the light emitting device optical axis is less than oneselected from 1 mm, 0.5 mm, 0.2 mm and 0.1 mm. In one embodiment of thisinvention, the standoffs are small beads or particles disposed in regionbetween the LRE and the lightguide. By using beads or particles that aresufficiently small, mechanically coupling between the LRE and lightguidecan occur without visible sight of the light extracting from the beadedregion. In one embodiment of this invention, the beads or domains havean average dimensional size less than one selected from the group of 200μm, 100 μm, 75 μm, 25 μm and 10 μm. In a further embodiment of thisinvention, the small beads or particles are dispersed between thelightguide and LRE such that the light extracted from the lightguide dueto the coupling from the beads creates a defined or random pattern ofhigher luminance regions at angles further from the light output surfacenormal. In a further embodiment of this invention, a light emittingdevice comprises a lightguide and a light redirecting optical elementoptically coupled to the lightguide in predetermined regions on thesurface of the lightguide. In a further embodiment, a first portion oflight in the lightguide is coupled out of the lightguide in the regionswhere the light redirecting element is optically coupled to thelightguide. The optically coupling in regions can be achieve throughpatterned adhesive deposition (such as ink jettype deposition systems,screenprinting systems and other systems suitable for depositingadhesives in a pattern) onto the lightguide and or the light redirectingelement and laminating them or pressing them together and curing ifnecessary. Other methods for optical coupling include laser welding inspecific regions, ultrasonic welding in specific regions, localizedthermal bonding and other techniques known in the glass and plasticbonding field to bond light transmitting materials.

LRE—Collimation Properties

One or more surfaces or region of a surface of the light transmittingmaterial, lightguide light redirecting element, light scatteringelement, or surface relief scattering element may include surfaceprofiles that provide collimation properties. The collimation propertiesdirect light rays incident from large angles into angles closer to thenormal (smaller angles) of at least one region of the light outputsurface of the light emitting device. The features may be in the form ofa linear array of prisms, an array of pyramids, an array of cones, anarray of hemispheres or other feature that is known to direct more lightinto the direction normal to the surface of the backlight. The array offeatures may be regular, irregular, random, ordered, semi-random orother arrangement where light can be collimated through refraction,reflection, total internal reflection, diffraction, or scattering.

LRE Surface-Relief Structure

One or more surfaces of the light redirecting element, lightguide, lightsource, or optical composite may contain a non-planar surface. Thesurface profile may contain protrusions or pits that may range from 1 nmto 10 mm in the x, y, or z directions. The profile or individualfeatures may have periodic, random, semi-random, or other uniform ornon-uniform structure. The surface features may be designed to providefunctions to the light redirecting element, such as collimation,anti-blocking, refraction, lightguide output coupling or extraction,symmetric diffusion, asymmetric diffusion or diffraction. In someembodiments, the surface features are a linear array of prismaticstructures that provide collimation properties. In another embodiment,the surface includes hemispherical protrusions that prevent wet-out orprovide anti-blocking properties or light-collimating properties.

LRE—Lenticular Lens

In one embodiment of this invention, the light redirecting element is alenticular lens array surface relief structure comprise a substantiallylinear array of convex refractive elements which redirect light from afirst angular range into a second angular range. In another embodimentof this invention, the light redirecting element is a light filteringdirectional control element comprising a lenticular element. As usedherein, a lenticular elements or structures include, but are not limitedto elements with cross-sectional surface relief profiles where thecross-section structure is hemispherical, aspherical, conical,triangular, rectangular, polygonal, or in the form of an arc or otherparametrically defined curve or polygon or combination thereof.Lenticular structures may be linear arrays, two-dimension arrays such asa microlens array, close-packed hexagonal or other two-dimensionalarray. The features may employ refraction along with total internalreflection such that the output angular range is less than the inputangular range within one or more light output planes. Lenticularstructures may also be used to redirect light to an angle substantiallyoff-axis from the optical axis of the element. As used herein,lenticular may refer to any shape of element which refracts or reflectslight through total internal reflection and includes elements referredto as “non-lenticular” in U.S. Pat. No. 6,317,263, the contents of whichare incorporated by reference herein. The lenticular structure may bedisposed on a supporting substrate. In one embodiment, the focal pointof the structures is substantially near the opposite surface of thesupporting substrate. The lenticular element may have a first focalpoint in the near field and a group of lenticular elements maycollectively have a far-field focal point defined as a region where thespatial cross-sectional area normal to the optical axis of the lightemitting device of the incident light flux is at a minimum. Thematerial, methods of making and structures of lenticular lens arrays,microlens arrays, prismatic films, etc. are known in the art of lightfixtures, backlights, projection screens and lenticular and 3D imaging.

In one embodiment of this invention, the light emitting device comprisesmore than one lenticular structure disposed on the same or opposite sideof a substrate. In one embodiment of this invention, a light emittingdevice comprises a light filtering directional control element wherein alenticular element disposed on the input surface can focus more lightthrough the light transmitting regions and change the direction or FWHMangular width of the light output profile from the light filteringdirectional control element. The structures can be convex or concave andsimilar to those used in double-lenticular rear projections screens suchas those described in U.S. Pat. Nos. 5,611,611, 5,675,434, 5,687,024,6,034,817, 6,940,644, and 5,196,960, the contents of each areincorporated herein by reference. The design of the lenticular shape onone or more surfaces is not limited to these features and includes otherdesigns known in the rear-projection screen and lenticular imagingindustry and the design may include lens, refractive, or reflectiveelements referenced in other patents referred to in other sections ofthis application and incorporated by reference herein.

Substantially clear lens substrates are known in the art and are used inthe production of lenticular screens for rear-projection screens. In oneembodiment of this invention, a volumetric diffuser is used as thesupporting substrate for a light redirecting element. In thisembodiment, the number of films may be reduced or the thickness reducesby alleviating or reducing the need for a substrate which is notoptically active and replacing it with a diffuser which improves theuniformity. By using an anisotropic volumetric diffuser (which scatterslight into higher angles in a first output plane parallel to thelenticules, and has very little or on effect on the scattering of lightalong the plane perpendicular to the lenticules), the focusing orcollimating power of the lenticular lens array in the second lightoutput plane perpendicular to the lenticules can be maintained while thespatial luminance uniformity of the light emitting device is improved.In one embodiment of this invention, the angular FWHM of the diffusionprofile of the anisotropic diffuser used as the lenticular lens arraysubstrate in the plane parallel to the lenticules is greater than oneselected from the group of 5, 10, 20, 30 and 50 and the angular FWHM ofthe diffusion profile of the anisotropic diffuser used as the lenticularlens array substrate in the plane perpendicular to the lenticules isless than one selected from the group of 10, 5, 4, 2, and 1. In afurther embodiment, the asymmetry ratio of the anisotropic lightscattering diffuser disposed as a substrate to the lenticular lens arrayin a light filtering directional control element is greater than oneselected from the group 5, 10, 20, 40, 50, and 60. Additionally, theFWHM of the total scattering angles in the first and second outputplanes of a light emitting device comprising the light filteringdirectional control element of one embodiment of this invention can beindependently controlled by use of an anisotropic diffuser. In a furtherembodiment of this invention, a light filtering directional controlelement within the light emitting device comprises a lenticular lensarray wherein the lenticular lenses have a conformal low refractiveindex region disposed on the curved surface of the lenticule such thatthe output surface is substantially planarized. In a further embodimentof this invention, the output surface of a planarized light filteringdirectional control element is the output surface, or a substantiallyco-planar surface coupled to a protective lens output surface of a lightfixture.

In another embodiment of this invention, a light redirecting elementcomprises a layer of beads, at least one of a light transmitting regionor light reflecting region disposed to refract incident light from alight transmitting region disposed between or substantially within in atleast one of the light transmitting or light reflecting regions.Analogous to the lenticular lens array, an array comprising a randomizedassortment of beads may be used to collimate or substantially reduce theangular extent of light exiting from a light transmitting region andfilter the light. The primary differences include the fact that the beadtype light filtering directional control element will reduce the angularextent of the output light in all planes of the output light normal tothe exiting surface. However, the ability to achieve very high levels ofcollimation is limited and the fill-factor, and ultimate transmission islimited due to the cross-sectional area limitations of close-packing anarray of spheres (or hemispheres or spheroidal lens-like structures). Inanother embodiment of this invention, a light filtering directionalcontrol element comprises lenticular or bead based elements and lighttransmitting regions and light absorbing regions in common with rearprojection screens such as those described elsewhere herein and thosedescribed in 6,466,368, except that when used with projection screens,the input light is typically collimated or of a reduced angular extentand is incident first upon the lenticular or bead elements and theoutput light is of a larger angular extent and exits through the lighttransmitting apertures. In one embodiment of the present invention, theincident light within a light emitting device on the light filteringdirectional control element has an angular FWHM greater than 30 degreesin a first plane and is incident first on the light transmitting regionsand the output light from the light filtering directional controlelement has a FWHM less than 30 degrees in the first plane and exitsthrough the lenticular or bead based refractive elements.

Common materials such as those used to manufacture lenticular screenssuch as vinyl, APET, PETG, or other materials described in patentsreferenced elsewhere herein may be used in the present invention for alight filtering directional control element. Light filtering directionalcontrol elements may comprise light transmitting materials. In a furtherembodiment, a material capable of surviving temperature exposures higherthan 85 degrees Celsius may used as the lenticular lens or substrate tothe lenticular lens or bead based element such as biaxially oriented PETor polycarbonate. By using a material capable of withstanding hightemperature exposure, manufacturing processes such as heating during apressure application stage or heating during an exposure stage may beused to decrease the production time.

In one embodiment of this invention a light emitting device comprises alenticular light redirecting element that collimates light such as a 90degree apex angle prismatic film. By pre-conditioning the light incidenton the light filtering directional control element, more light istransmitted and the FWHM angular output angles of the light emittingdevice along one or more output planes is reduced relative to a lightemitting device comprising just the light filtering directional controlelement. In one embodiment of this invention, a light emitting devicecomprises two crossed 90 degree prismatic collimating films and a lightfiltering directional control element such that the angular width of theFWHM intensity profile within one light emitting device output plane isless that 15 degrees. In a additional embodiment of this invention, alight emitting device comprises two crossed 90 degree prismaticcollimating films and a light filtering directional control element suchthat the angular width of the FWHM intensity profile within one lightemitting device output plane is less that 10 degrees. In anotherembodiment of this invention, a light emitting device comprises twocrossed 90 degree prismatic collimating films and a light filteringdirectional control element such that the FWHM along one light emittingdevice output plane is less than 8 degrees. In another embodiment ofthis invention, a light emitting device comprises a light filteringdirectional control element, a first 90 degree prismatic collimatingfilm and a second 90 degree prismatic film providing brightnessenhancement with anisotropic light scattering phase domains dispersedwithin the substrate as describe in U.S. patent application Ser. No.11/679,628, the contents of which is incorporated herein by reference.In the previous embodiment, the angular width of the FWHM intensityprofile within one light emitting device output plane is less than oneselected from the group of 8 degrees, 10 degrees, 15 degrees or 20degrees. In another embodiment of this invention, a light emittingdevice comprises a 90 degree prismatic collimating film disposed above alight filtering directional control element wherein the prisms areoriented substantially orthogonal to the lenticules and furthercomprises a second 90 degree prismatic film disposed on the oppositeside of the light filtering collimating film providing brightness anduniformity enhancement with anisotropic light scattering phase domainsdispersed within the substrate and a lightguide and at least one lightemitting diode. In one embodiment of this invention, the use of at leastone brightness enhancing or collimating film along with a lightfiltering directional control element which comprises a light absorbingregion permits more light to pass through the light filteringdirectional control element due to the more highly collimated incidentlight profile upon the light filtering directional control element. Inone embodiment of this invention, a light emitting device comprises alight redirecting element that is a collimating film selected from thegroup of BEF, BEF II, BEF III, TBEF, BEF-RP, BEFII 90/24, BEF II 90/50,DBEF-MF1-650, DBEF-MF2-470, BEFRP2-RC, TBEF2 T 62i 90/24, TBEF2 M 65i90/24, NBEF, NBEF M, Thick RBEF, WBEF-520, WBEF-818, OLF-KR-1, and 3637TOLF Transport sold by 3M, PORTGRAM V7 sold by Dai Nippon Printing Co.,Ltd., LUMTHRU that sold by Sumitomo Chemical Co., Ltd., ESTINAWAVE W518and W425 DI sold by Sekisui Chemical Co., Ltd, and RCF90 collimatingfilm sold by Reflexite Inc.

The light emitting device may also comprise a light redirecting elementthat re-directs a substantially portion of the light into an off-axisorientation. In one embodiment of this invention, a light emittingdevice comprises a non-symmetrical prismatic film such as a ImageDirecting Film (IDF or IDFII) or Transmissive Right Angle Film (TRAF orTRAFII) sold by 3M. In one embodiment of this invention, a wall washinglight fixture comprises a non-symmetrical prismatic film. In oneembodiment of this invention, a light emitting device comprises asymmetrical prismatic film to re-distribute the light symmetricallyabout an axis such as a prismatic film with a 60 degree apex angle withthe prisms oriented toward the output surface. In other embodiment ofthis invention, a light emitting device comprises a lenticular lensarray, a light reflecting region, light transmitting regions, and alinear prism film with an apex angle between 45 degrees and 75 degreeswhere the substrate of the linear prism film is coupled directly orthrough another layer to the light reflecting regions with the prismsoriented away from the lenticules. In another embodiment of thisinvention, the linear prism film or light redirecting element is a“reverse prism film” such as sold by Mitsubishi Rayon Co., Ltd. underthe trade names of DIA ART H150, H210, P150 and P210, or is a prismaticfilm of a similar type as disclosed in the embodiments within U.S. Pat.Nos. 6,545,827, 6,151,169, 6,746,130, and 5,126,882, the contents ofeach are incorporated by reference herein.

LRE—Pitch

The pitch of the light redirecting element or lenticular lens structurewill have an effect on the focusing power, the thickness of thelenticular lens array and substrate and other optical properties such asmoiré. In one embodiment of this invention, the lenticular lens arraystructure is in the form of concentric lenticular lenses. In thisembodiment, the lenses are parallel, but are arranged in an arc orcircle. The pitch of the lenses and other properties may vary similarlyto linear lenticular lenses. A light emitting device comprising a lightfiltering directional control element comprising concentric lenticularlenses can provide a spatial filtering along radial directions asopposed to linear directions. In one embodiment of this invention, alight emitting device comprising a substantially centrally located lightsource and a light filtering directional control element comprising aconcentric lenticular lens has a spatial luminance uniformity greaterthan one selected from 60%, 70%, 80% and 90%. The concentric lenticularlens may be manufactured using injection molding, stamping, embossing orother similar techniques known in the optical industry suitable formaking Fresnel lenses. In one embodiment of this invention, a lightfiltering directional control element, or light emitting devicecomprising the same, comprises a concentric lenticular lens array and atleast one of a light reflecting, light absorbing, or light transmittingregion wherein the regions are substantially ring or arc-shapedcorresponding to the concentric lenticular lens.

Light Redirecting Element (LRE) Alignment

In an additional embodiment of this invention, the alignment of thelight redirecting element is rotated with respect to an exit aperture ofthe light emitting device. In one embodiment, the light redirectingelement is aligned at an angle φ1 to the longer dimension of the lightexiting aperture of the light emitting device. In an additionalembodiment, φ1 is one selected from the group consisting of 0 degrees,45 degrees, and 90 degrees. In another embodiment of this invention, alight emitting device comprises a light filtering directional controlelement wherein the lenticular lens array is aligned at an angle φ2relative to a 90 degree apex angle prismatic collimating film wherein 90degrees>φ2>0 degrees and the contrast of the spatial luminance moirépattern of the light fixture is less than one selected from the groupconsisting of 0.8, 0.5, 0.2, 0.1 and 0.05.

Light Output Surface

In one embodiment of this invention, a light emitting device comprises alightguide and at least one light output surface. The light outputsurface, or light emitting surface, comprises the last optical elementsfrom which the light leaves the light emitting device. In one embodimentof this invention, the light output surface comprises at least oneselected from a light scattering lens, lightguide, light reflectingelement, reflector, housing, volumetric light scattering element,diffuser surface relief diffuser, optical film, substrate, substantiallytransparent lens or protective or holding cover material, and glasslens. The light output surface may be planer, curved, domed, arcuate,quadric, radially symmetric, more than half of a sphere, or othersurface shape. A light emitting device may comprise more than one lightoutput surface. For example, an edge-lit lightguide may emit lightsubstantially in opposite directions from opposite planar light outputsurfaces. The light output surface may comprise more than one lightguidein a light emitting device and may include a reflector or transparent,non-scattering lens.

Light Filtering Directional Control Element (LFDCE)

In one embodiment of this invention, a light emitting devices comprisesa light redirecting element that is a Light Filtering DirectionalControl Element (LFDCE). In one embodiment of this invention, a LFDCEcomprises a light transmitting layer disposed between lenticularelements and a first input surface. In another embodiment of thisinvention, a LFDCE comprises a light transmitting layer disposed betweenmicrolens array elements and a first input surface. In one embodiment ofthis invention, a light emitting device comprises a light filteringdirectional control element (LFDCE) with a first input surface disposedto receive light and an first output surface disposed to output lightwherein the light filtering directional control element collimates thelight within a first plane and the light emitting device furthercomprises an anisotropic light scattering element disposed in theoptical path after the first light output surface and has a higherangular FWHM diffusion profile in the first plane than in a second planeorthogonal to the first. In this embodiment, the light filteringdirectional control element, filters out the unwanted non-uniformitiesof the incident light in a very thin profile and substantiallycollimates the incident light (such as providing an output light with anangular FWHM of less than 10 degrees FWHM in the first output plane).The anisotropic diffuser can be provided with a range of angles toprovide a customizable light output profile. In one embodiment of thisinvention, a light emitting device with an angular FWHM of less than 10degrees in at least one output plane and an anisotropic light scatteringfilm is provided as a kit wherein the combination of the two provides apre-determined light output profile.

In another embodiment of this invention, the portion of incident lighton the light reflecting region side of the light filtering directionalcontrol element which is not reflected is substantially absorbed by thelight absorbing region. In a further embodiment of this invention, thelight reflecting region reflectively scatters light anisotropically intoa larger angular FWHM in the plane perpendicular to the lenticules thanparallel to the lenticules due to scattering from the asymmetricallyshaped disperse phased domains oriented with their larger axissubstantially parallel to the lenticules. By reflectively scattering thelight more in the plane perpendicular to the lenticules, the light willmore likely reach a neighboring light transmitting region through fewerbounces and reflections from the light reflecting region. Since thelight reflecting region is less than 100% reflective and some light iseither absorbed in the light reflecting region or passes through (intoundesirable angles or into a light absorbing region where it can beabsorbed), it is desirable for the light to travel through thelightguide such that it will reach a neighboring aperture through aminimal number of reflections from the light reflecting region.

In one embodiment of this invention, a light filtering directionalcontrol element comprises a lenticular lens array and a light reflectingregion comprising asymmetrically shaped disperse phase domains thatreflectively scatter anisotropically such that the angular FWHM of thelight scattering in the plane perpendicular to the lenticules is greaterthan the angular FWHM of the light parallel to the lenticules, and lighttransmitting regions disposed near the focus of the lenticules such thatlight transmitted through the light transmitting apertures has a smallerangular FWHM than the light incident on the light filtering directionalcontrol element. In a further embodiment, a light emitting devicecomprises the light filtering directional control element of thepreviously described embodiment.

In one embodiment of this invention, a light emitting device comprises alinear array of LED's illuminating a lightguide from a least twoopposing sides of a lightguide through the edges. In another embodimentof this invention a light filtering directional control elementcomprises a lenticular lens array disposed on a substrate, lightreflecting regions disposed on the other side of the substrate than thelenticules, light transmitting regions disposed to filter and transmit aportion of light incident to the lenticular lens array from the lightreflection region side and a lightguide wherein the light reflectingregion is adhered to the lightguide and the lightguide comprises atleast one selected from the group of light extraction features, ananisotropic light scattering region, and a spatially modified reflectiveregion (departure in one or more regions from a regular linear array ofclear apertures to an array of dots for example) to provide increaseduniformity and light extraction from the lightguide. In one embodimentof this invention, a light emitting device comprises a light filteringdirectional control element comprising a reflective region that defineslight transmitting apertures that vary in length and width in thedirections parallel and perpendicular to the lenticules and are disposedsubstantially near the optical axes of the lenticules such that thelight exits the lightguide through the apertures and exits the lightemitting device within an angular FWHM of less that 70 degrees in atleast one output plane.

In another embodiment of this invention, the first light transmittinglayer has a diffuse reflectance measured in the d/8 geometry with thespecular component included of greater than 70%. In another embodimentof this invention, the light blocking region is a light reflectionregion and the diffuse reflectance of the light reflecting region, DR,is greater than 70% as calculated by

${DR} = \frac{DRT}{\left( {1 - {ART}} \right)}$where DRT is the total diffuse reflectance of the light transmittinglayer measured in the d/8 geometry with the specular component includedand ART is the percentage area ratio of the total of the light blockingand light transmitting regions that is occupied by the lighttransmitting region.

In another embodiment of this invention, the first light blockingregions absorb light and the diffuse reflectance of the lighttransmitting layer measured in the d/8 geometry with the specularcomponent included is less than 20%. In one embodiment of thisinvention, the first light blocking regions are light absorbing regionsand the light transmitting layer further comprises light reflectingregions disposed substantially in-between the light absorbing regionsand the input surface. In one embodiment of this invention, the lightreflecting regions comprise a volumetric anisotropic light scatteringelement.

In a further embodiment of this invention, the pitch of the first groupof lenticular elements is equal to the pitch of the second group oflenticular elements and the width of the first light transmittingregions is not equal to the width of the second light transmittingregions in a first direction orthogonal to the first optical axes.

In a further embodiment of this invention, a fixture comprises a lightfiltering directional control element comprising the light outputsurface of the light emitting device, an optical lightguide, and a whitediffusely reflecting film opposite the light output side of thelightguide.

In one embodiment of this invention the light filtering directionalcontrol element comprises: an input surface; an output surface; firstlight transmitting regions; first light blocking regions; lenticularelements formed in a first light transmitting material; a first group oflenticular elements with first lenticular apexes and first optical axes;a light transmitting layer disposed in an optical path between the inputsurface and the first group of lenticular elements comprising the firstlight blocking regions disposed in-between the first light transmittingregions; a first angle gamma, defined as the angle between the lineformed between the apexes of the first group of lenticular elements andthe center of the light transmitting regions and the optical axes of thefirst group of lenticular elements; a lightguide comprising lightextraction features disposed to receive light from the input surface andtransmit light to the first light transmitting layer; wherein the firstgroup of light blocking regions are disposed to intersect the opticalaxes of the first group of lenticular elements and gamma is greater than5 degrees. In a further embodiment of this invention, a light emittingdevice comprises the light filtering directional control element of theprevious embodiment with a peak angle of illuminance greater than 0degrees from the light output surface.

In a further embodiment of this invention, a light emitting devicecomprises a light filtering directional control element and a luminairedevice disclosed in an embodiment of U.S. Pat. No. 5,594,830, thecontents of which are incorporated by reference herein.

LFDCE—Light Transmitting Layer

In one embodiment of this invention, a LFDCE comprises a lighttransmitting layer disposed between lenticular elements and a firstinput surface. The light transmitting region may comprise light blockingregions and light transmitting regions. The light blocking regions maybe light absorbing, light reflecting, partially light absorbing,partially light reflecting or a combination thereof. The lighttransmitting layer may comprise a light blocking region comprising alight absorbing region disposed between a light reflecting region andthe lenticular elements. The light reflecting regions may be diffuselyreflective or specularly reflective and the light transmitting regionsmay be specularly transmitting or diffusely transmitting. A lightabsorbing region or light blocking region, as used herein, may include aregion that absorbs a first portion of light and transmits or reflects asecond portion of light. A light reflecting or light blocking region, asused herein, may include a region that reflects a first portion of lightand transmits or absorbs a second portion of light.

LFDCE—Light Transmitting Regions

The light transmitting regions permit light from a specific spatialregion to be transmitted through to the lenticular lens array. In orderto provide a light filtering directional control element with high lightthroughput efficiency, a sufficient amount of light must be able to betransmitted through the light transmissive regions. In one embodiment ofthis invention, the total luminous transmittance of the clear lighttransmitting regions measured according to ASTM D1003 before theapplication of the light blocking regions is at least one of 50%, 70%,80%, 85%, 90%, 95% when measured with the incident light passing throughthe lenticular lens before the transmissive aperture region. In oneembodiment of this invention, the aperture region is diffuselytransmissive such that the light is diffused as it passes through theaperture region. In one embodiment of this invention, the haze of the ofthe clear aperture regions measured according to ASTM D1003 with a BYKGardner Hazemeter before the application of the light blocking regionsis at least one of 5%, 10%, 20%, 50%, 80%, 90%, or 99% when measuredwith the incident light passing through the lenticular lens before thetransmissive aperture region. In another embodiment of this invention,the aperture region comprises an anisotropic light scattering region.The anisotropic light scattering region transmits and scatters lightanisotropically to provide improved uniformity and a predeterminedangular light distribution performance. In a further embodiment of thisinvention, the asymmetry ratio of the FWHM diffusion profiles of theanisotropic light scattering region is greater than one selected fromthe group consisting of 2, 5, 10, 30, 50, and 60.

The width of the light transmitting region is selected to provide apredetermined light output angular profile while maintaining asufficient level light filtering and light transmission through thelight filtering collimating lens. The fill factor is defined as theratio of the light transmitting region width to the width of the lightabsorbing or reflecting region between the apertures along a first axisparallel to the array of lenticules. In order for the light filteringcollimating lens to provide a high degree of collimation, theCollimation Factor, CF, should be sufficiently high assuming a constantfocal point, lens shape and refractive index. The Collimation Factor isa relational metric used to compare the ability of a lenticular lensarray to collimate light from a specific light transmitting regionassuming a constant lenticule curvature and focal distance. TheCollimation Factor is defined as the ratio of the pitch of thelenticular lens P1, to the aperture width, A1, or P1/A1. In oneembodiment of this invention, the pitch of the lenticular lens isapproximately 187 μm, the aperture width of the light transmittingregion is 25 μm and the linewidth of the light absorbing (or reflecting)region is 162 μm and the CF is 6.5. In one embodiment of this invention,the CF is greater than one element selected from the group consisting of1.5, 3, 5, 6, 8 and 10.

The location of the aperture in relation to the lenticular lens elementsor arrays determines the directionality of the output light. In oneembodiment of this invention, the aperture is centered along the opticalaxis of the lenticules in an optical element. In another embodiment ofthis invention, the light output distribution is off-axis and is definedby an angle, γ1, defined from the apex of the lenticule to the center ofthe apertures and measured from the normal of the substantially planaroptical element. In one embodiment of this invention, the angle γ1 isgreater than one angle selected from the group comprising 5°, 10°, 15°,20° 30° and 40°. In one embodiment of this invention, a light emittingdevice comprises a light filtering directional control element whereinγ1 is greater than 5 degrees and the angle of peak intensity of lightoutput from the light emitting device is at an angle θ1 measured from anormal to the light output surface of the light emitting device where θ1is greater than 0 degrees. In another embodiment of this invention, θ1is greater than 5 degrees and the light emitting device is awall-washing type light fixture wherein less light is directed into theroom directly and more light is directed onto the wall than is the casewhen θ1=0 degrees. In one embodiment of this invention, the lightfiltering directional control element (or light emitting devicecomprising the same) has a positive far-field focus greater than a firstlinear dimension of the light output surface. In one embodiment of thisinvention, the light filtering directional control (or light emittingdevice comprising the same) has a positive far-field focus less than afirst linear dimension of the light output surface. As used herein,far-field refers to the distance from the light emitting device lightoutput surface that is greater than at least 10 times the separation ofthe smallest separation between the lenticular elements. In a furtherembodiment of this invention, the aperture is located substantially nearthe midpoint between the lenticules. In this embodiment, upon wide angleinput illumination, the light filtering directional control elementproduces a twin-lobe output with two maximums intensities. In a furtherembodiment of this invention, the angular intensity profile resemblesthat of a batwing light distribution such as commonly desired for in alight fixture to provide a uniform illuminance distribution.

In one embodiment of this invention, the angular light output profile ofthe light filtering directional control element or light emitting deviceis controlled by spatially varying at least one of the size, shape,pitch, and transmittance of the light transmitting apertures. By havingregions, with wider apertures, for example, the light output from thatregion will have a lower degree of collimation and higher flux outputthrough less recycling. This technique may be used to spatially adjustthe uniformity of light emitting device. In one embodiment, anedge-illuminated light emitting device comprises a light filteringdirectional control element wherein the aperture width increases in theregion the further the distance from light source lightguide entranceedge. In this embodiment, the method used to create the linewidths of atleast one of the light blocking, light reflecting, light absorbing, orlight transmitting regions can be used to improve the spatial luminanceuniformity of the light emitting device. Additionally, the angularoutput in different regions may be controlled more easily by increasingthe aperture width in some regions and reducing the aperture width alongat least one axis in order to provide a light emitting device with aprecisely tailored output profile. In one embodiment of this invention,the angular output in different spatial regions is varied by adjustingthe locations of the apertures or light transmitting regions in a firstdirection in a first plane relative to the optical axes of thecorresponding lenticular elements where the first plane is perpendicularto the optical axes.

In one embodiment, the angular output from a light emitting device oroptical element is modified in one or more regions by converting it to aspatial adjustment in the printing, transfer, exposure, etc. method usedto create the size or location of lines, patterns circular holes, etc.and thus apertures. In another embodiment of this invention, at leastone of the linewidth and location relative to the optical axis of itsrespective lenticule of the light transmitting region varies along adirection parallel to the lenticular array to provide a focusing orconcentrating affect to the light output profile. As discussed herein,by shifting the light transmitting region to one side of the axis of alenticule, light can be directed off-axis. By shifting the lighttransmitting regions spatially in two opposite regions in away from eachother in different areas of a light emitting device, the light exitingthe lenticules from those corresponding regions can be directed toward aspecific location off-axis at an angle theta, thus essentially creatinga positive focal point for the light output. In the case where the lighttransmitting regions move closer towards each other, the light outputfrom the corresponding lenticular lens array regions diverges relativeto each other, thus creating a type of negative, or virtual focus.

In one embodiment of this invention a light filtering directionalcontrol element comprises an input surface, an output surface, firstlight transmitting regions, first light blocking regions, a first groupof lenticular elements formed in a first light transmitting materialwith first lenticular apexes and first optical axes, a lighttransmitting layer disposed in an optical path between the input surfaceand the first group of lenticular elements comprising the first lightblocking regions disposed in-between the first light transmittingregions, a first angle γ, defined as the angle between the line formedbetween the apexes of the first group of lenticular elements and thecenter of the light transmitting regions and the optical axes of thefirst group of lenticular elements wherein the first group of lightblocking regions are disposed to intersect the optical axes of the firstgroup of lenticular elements and γ is greater than 5 degrees, a secondgroup of lenticular elements formed in the first transmitting materialwith second lenticular apexes and second optical axes, and furthercomprises: a second light blocking regions disposed in the first lighttransmitting layer, second light transmitting regions disposed in thefirst light transmitting layer and in-between the second light blockingregions, a second angle δ1, defined as the angle between the line formedbetween the apexes of the second group of lenticular elements and thecenter of the second light transmitting regions and the second opticalaxes of the second group of lenticular elements, wherein γ is not equalto δ1. In one embodiment of this invention, the optical elementcomprises a lenticular element with different groups of lighttransmitting regions that vary in their location with respect to thecorresponding optical axes of the lenticular elements. By varying therelative locations of the light transmitting apertures, the far-fieldangular light output can be controlled to provide a far-field focalpoint and off-axis directionality.

In one embodiment of this invention, a substantially planar lightemitting device comprises a light filtering direction control elementwith a positive focal distance. In one embodiment of this invention, asubstantially planar light emitting device comprises a light filteringdirection control element with a negative focal distance. A positive ornegative focal distance can be used in a light emitting device toprovide increased control over the light output and can be used toconcentrate or further spread out light within one or more outputplanes.

In one embodiment of this invention, the angular light output profile ofthe light filtering directional control element or light emitting devicecomprising the same is controlled by spatially varying at least one ofthe size, shape, pitch, and transmittance of the lenticular elementsand/or the light transmitting regions.

LFDCE—Light Reflective Region

In one embodiment of this invention, light reflecting regions aredisposed substantially in-between the light transmitting apertureregions in a light filtering directional control element. The reflectiveregions may be diffusely reflective or specularly reflective and thediffusely reflective profile may be symmetric or anisotropic. Typicallyin light fixtures, the light reaching the optical elements arrives froma wide range of angles and therefore, the diffuse luminance reflectancemeasured in a d/8 geometry (shortened here to diffuse reflectance) is amore representative measurement of the reflectance from the component ina light fixture application than 1 minus the specular transmittance suchas defined and sometimes measured according to the ASTM D1003 standard.The diffuse reflectance of an element, region, or combination of regionscan be measured placing the element or region(s) over an aperture of a“dark box” wherein the interior is filled with light absorbing materialsuch as a black felt and measuring the diffuse reflectance (specularcomponent included) of the element using a Minolta CM-508d diffusereflectance meter.

A diffusely reflecting region as defined herein is one wherein 532 nmlaser light with a divergence less than 10 milliradians incident uponthe region reflects with a larger angular intensity diffusion profilesuch that the FWHM of the diffuse reflecting intensity profile isgreater than 2 degrees within at least one plane of reflection. In oneembodiment of this invention, the diffusely reflecting regionanisotropically reflects light such that the angular FWHM of thereflected intensity profile is higher in a first reflectance outputplane than a second reflectance output plane orthogonal to the first. Inone embodiment of this invention, a light filtering directional controlelement comprises light reflecting regions of an anisotropicallyreflecting diffuser with a FWHM diffusion profile of at least 5 degreeswithin a first reflecting plane and an asymmetry ratio of greaterthan 1. In this embodiment, the light transmitting apertures aredisposed between the anisotropic light scattering regions. In anotherembodiment of this invention, a light filtering collimating lenscomprises light reflecting regions of an anisotropically reflectingdiffuser with a FWHM diffusion intensity profile of at least 5 degreeswithin a first reflecting output plane and an asymmetry ratio of greaterthan 1 wherein the diffusely reflecting output plane with the largerFWHM angular intensity diffusion profile is oriented perpendicular tothe lenticules in the lenticular lens array. In this embodiment, thelight reflected from the anisotropically reflecting regions is moreefficiently directed angularly toward the clear apertures wherein morelight may pass through the light transmitting apertures than in the caseof a symmetrically diffusing light reflecting region wherein light isadditionally diffused in a direction parallel to the lenticules andparallel to the diffusely reflecting region. In the case of thesymmetrically diffusing light reflecting region, light scatteringparallel to the reflecting regions will require significantly morereflections in order to exit through the light transmitting apertures.These multiple reflections cause more of the light to be absorbed withinthe materials.

In one embodiment of this invention, a light filtering directionalcontrol element comprises a substantially diffusely reflecting region.In a further embodiment of this invention, a light emitting devicecomprises a light filtering directional control element withsubstantially transparent regions disposed between light reflectingregions wherein the diffuse reflectance of the light filteringdirectional control element is greater than one selected from the groupconsisting of 40%, 50%, 60%, 70%, 80%, 90%, and 95% when measured withdiffusely incident light on the side of the lenticular lens arraycomprising the light reflecting region.

The light transmitting regions can reflect a portion of the incidentlight in a specular, symmetrically diffuse, or anisotropic scatteringreflecting profile. In light filtering directional control elementscomprising light reflecting regions and light transmitting regions whichare partially transmitting and partially reflecting, the reflectancefrom the combination will increase the luminance and color uniformitywhen used in a light emitting device. In one embodiment of thisinvention, a light emitting device comprises a light filteringdirectional control element with partially transparent regions disposedbetween diffusely reflecting regions wherein the diffuse reflectance ofthe combination of the light reflecting region and the lighttransmitting region is greater than one selected from the groupconsisting of 40%, 50%, 60%, 70%, 80%, 90%, and 95%. In one embodimentof this invention, a light emitting device comprises a light filteringdirectional control element with light transmitting regions disposedbetween light reflecting regions wherein the light transmitting regionshave a diffuse reflectance greater than 10% and the diffuse reflectanceof the combination of the light reflecting region and the lighttransmitting apertures is greater than 80%. In this embodiment, morelight is recycled than in the case of substantially transparent or lowreflectance light transmitting regions and therefore the luminance andcolor uniformity of a light emitting device incorporating the element isimproved while still providing a sufficient amount of light to passthrough the apertures and exit the light emitting device. In a furtherembodiment of this invention, a light emitting device comprises a lightfiltering directional control element with a lenticular lens array andlight reflecting regions disposed in-between light transmitting regionswherein the light transmitting regions contain asymmetric particles andthe reflected light from the light transmitting region is reflectedanisotropically and the diffuse reflectance of the light transmittingregion is greater than 10% and less than 80%.

In another embodiment of this invention, a light emitting devicecomprises a light filtering directional control element comprising alenticular lens array and light transmitting regions disposed betweenlight reflecting regions wherein the diffuse reflectance of the lightreflecting region and the light transmitting region is greater than oneselected from the group consisting of 40%, 50%, 60%, 70%, 80%, 90%, and95%.

In light filtering directional control elements which have lighttransmitting regions made of substantially transparent material wherethe total luminous transmittance is greater than approximately 92%(including Fresnel reflections), the diffuse reflectance of the lightreflecting regions disposed between the light transmitting regions canbe calculated. The diffuse reflectance of the light reflecting regionDR_(LR) can be calculated by dividing the diffuse reflectance of thetotal of both regions (DR_(T)) by the area ratio of the light reflectingregion, 1−AR_(T) where AR_(T) is the percentage of area of the totalregion occupied by the light transmitting region and thus the diffusereflectance of the light reflecting region, DR_(LR)=DR_(T)/(1−AR_(T)).In another embodiment of this invention, a light emitting devicecomprises a light filtering directional control element which comprisesa lenticular lens array and light transmitting regions disposed betweenlight reflecting regions wherein the diffuse reflectance of the lightreflecting regions is greater than one selected from the groupconsisting of 80%, 90%, and 95% as measured by the aforementionedmethod.

In one embodiment of this invention, the diffuse reflectance of thediffusely reflecting regions is less than 95% such that more than 5% ofthe light is transmitted through the diffusely reflecting regions. Byincreasing the light transmittance (lowering the diffuse reflectance),light is transmitted at the higher angles from the normal in addition tothe light passing through the clear apertures which is more collimated.The light transmitting through the diffuse regions will lower the moirécontrast between the light filtering directional control element andanother optical element in the system. In one embodiment of thisinvention, the light output profile of a light emitting devicecomprising a light filtering directional control element has a softerangular cut-off due to the diffusely reflecting regions having a lighttransmittance greater than 5%. In a further embodiment of thisinvention, the light output profile of a light emitting devicecomprising a light filtering directional control element comprisingreflecting regions having a light transmittance greater than 5% has anangular output region with a slope of less than one selected from thegroup of 10% per degree, 5% per degree, 2% per degree, and 1% per degreewhere the % drop refers to the percentage of the intensity relative tothe peak intensity in the angular region between the peak intensity andthe angular points at 10% intensity within at least one output plane.

LFDCE—Mirror Mode

In a further embodiment of this invention, a light emitting devicecomprises a light filtering direction control element comprising aspecularly reflecting region wherein the light emitting device hasspecularly reflective properties similar to a mirror in at least one ofa spatial region, angular region, and period of time (switchable to amirror mode). In one embodiment of this invention, the specularlyreflecting region allows the light emitting device to serve as a mirrorwhen the light emitting device is off and the light filteringdirectional control element serves to recycle and provided increaseduniformity in a small form factor (reduced total thickness of the lightemitting device) as well as reducing the angular output of light suchthat the output light is more collimated. In a further embodiment ofthis invention, a light emitting device comprises a light filteringdirectional control element with a specularly reflective region whereinthe fill factor of the specularly reflective region is greater than 50%area such that the display can be used as a mirror as well as a lightemitting device simultaneously. This can allow the elimination ofshadows on a mirror viewer's face and can reduce the form factor by notneeding an additional, separate light source near one or more of theedges, and can also assist portability. In a further embodiment of thisinvention, a lighted mirror comprises a light filtering directionalcontrol element comprising a lenticular lens array, a specularlyreflecting region and light transmitting regions between the lineararrays of the light reflecting regions such that the fill factor of thespecularly reflecting regions is greater than 75%. In a furtherembodiment, the width of the light transmitting apertures is less than100 microns such that the individual bright lines are not readilydiscernable when emitting light.

In a further embodiment, the light emitting device with a mirror modefurther comprises red, green, and blue LED's such that the color of thelight output can be adjusted to match a desired illumination color (suchas fluorescent office lights, halogen lights, or daylight or a cloudyday). This is useful for a user to discern their appearance (makeup,clothes, etc.) in the expected illuminant color for the day. Theintensity may also be adjusted such that the brightness is at a pleasinglevel. By being able to illuminate the viewer at an angle closer to orat the normal to the mirror, fewer or no shadows are visible in contrastto light disposed along the edges of a mirror. In a further embodiment,the regions corresponding to the viewers eyes has reduced lighttransmission by at least one of increasing the width of the lightreflecting lines and reducing the transmission of the light transmittingapertures. In a further embodiment of this light emitting device with amirror mode, the light output is collimated to an angular width of lessthan 15 degree FWHM in at least two orthogonal planes such that less ofthe light output in the regions distant from the viewers eyes will notreach their eyes and result in glare when viewing in the mirror mode.

LFDCE—Light Blocking and Light Transmitting Region

In one embodiment of this invention, the light filtering directionalcontrol element comprises light absorbing and light transmitting regionsdisposed in a light transmitting layer substantially in-between lighttransmitting apertures or regions. Some methods of manufacturing limitthe diffuse reflectance of a light reflecting regions (such as in thecase of a mostly reflecting, partially transmitting light reflectingregion) to less than 90%. The light transmitted through the reflectiveregions is less collimated in some configurations and as a result theangular spread of light may be larger than desired. In one embodiment ofthis invention, a light absorbing region is disposed between thelenticules and the light reflecting region, and substantially over thelight reflecting regions. In this embodiment, the light absorbingregions will absorb a substantial amount of residual light transmittedthrough the light reflecting regions. In another embodiment of thisinvention, the light reflecting layers reflect a portion of incidentlight such that the uniformity of the incident light pattern isincreased without absorbing a significant amount of light that wouldprohibit recycling and increase light output.

In a further embodiment of this invention, a light emitting devicecomprising a light filtering directional control element with a lightabsorbing region disposed between the lenticules and a light reflectingregion has a diffuse reflectance measured from the light exiting surfaceof the light emitting device of less than one selected from the group of80%, 60%, 40% 30%, 20%, 10% and 5%. In a further embodiment of thisinvention, a light emitting device comprising a light filteringcollimating lens has a diffuse reflectance of less than 20% and appearssubstantially black when viewed in a first angular range in theoff-state and the on-state. In some applications, it is desirable tominimize ambient light reflections (in the on, off or both states) fromthe light fixture such as in movie theaters, airplane cockpits, etc. Byemploying a light absorbing region along with a light reflecting region,the recycling due to the light reflecting region and the lighttransmitting apertures provides the increased efficiency, uniformity andangular control, while the light absorbing regions provide reducedambient light reflections and lower transmittance above the lightreflecting regions which can reduce light levels in the predeterminedangular range.

Light emitting devices with high efficiencies may often appear non-whitesuch as silver or gray. This can occur because optical elements such asdiffusers with high forward light transmission for efficiently directinglight from inside the fixture to the appropriate angles and uniformityprofiles outside of the fixture do not reflect ambient light. By notreflecting ambient light, the fixtures, when not turned on, often have agray or silver appearance depending on the remaining optical elementswithin the fixture. In one embodiment of this invention, a lightemitting device has a sufficient diffuse luminous reflectance of ambientlight while maintaining a high luminous transmittance of light from thelight filtering collimating lens. The diffuse reflectance of the lightemitting device can be measured in a (d/8 geometry) using a MinoltaCM-508d with the specular component included and measuring thereflectance from the light exiting surface on the light exiting side.The forward luminous transmittance of the light filtering directionalcontrol element used in a light emitting device can be measured byaccording to ASTM D1003 measured with the light incident on the diffusereflecting side of the light filtering directional control element. Inone embodiment of this invention, a light filtering directional controlelement has a diffuse reflectance measured on the light exiting surfaceof greater than 30% and a forward luminous transmittance of greater than50%. In another embodiment of this invention, a light filteringdirectional control element has a diffuse reflectance measured on thelight exiting surface of greater than 20% and a forward luminoustransmittance of greater than 40%. In another embodiment of thisinvention, the optical system efficiency of a light emitting deviceincorporating a light filtering directional control element is greaterthan 60% as measured comparing the light source flux output and the fluxoutput of a light emitting device incorporating the same light source ina sufficiently large integrating sphere according to IES LM-79-80standard.

In another embodiment of this invention, the reflected color of thelight emitting device output surface sufficiently matches that of thehousing. In some environments, it is desirable to match the color of thelight emitting device housing to the light emitting surface. Normally,this is difficult to achieve without introducing a light absorbingfilter into the path which significantly reduces the output luminousflux of the fixture. In one embodiment of this invention, a lightemitting device comprises a light filtering collimating lens with alight absorbing region disposed between a lenticular lens array and alight reflecting region wherein the light absorbing region has a colordifference from a region of the light emitting device housing of Δu′v′of less than 0.1 on the 1976 u′, v′ Uniform Chromaticity Scale asdescribed in VESA Flat Panel Display Measurements Standard version 2.0,Jun. 1, 2001 (Appendix 201, page 249) and measured with a MinoltaCM-508d spectrometer under d/8 conditions, specular component included.In another embodiment of this invention, a light emitting devicecomprising a light filtering directional control element has a colordifference Δu′v′ of less than 0.04 between at least one region of thelight emitting surface and at least one region of the housing. Inanother embodiment of this invention, a light emitting device comprisesa light filtering directional control element wherein the differencebetween the diffuse reflectance of at least one region of the lightemitting surface and at least one region of the housing is less than20%. In a further embodiment of this invention, a light emitting devicecomprises a light filtering directional control element wherein thedifference between the diffuse reflectance of at least one region of thelight emitting surface and at least one region of the housing is lessthan 10%. In a further embodiment of this invention, a light emittingdevice comprises a light filtering directional control element whereinthe difference between the diffuse reflectance of at least one region ofthe light emitting output surface and at least one region of the housingis less than 20% and the color difference Δu′v′ is less than 0.2. In oneembodiment of this invention, the difference (Δu′v′) between theintegrated light output color of a light emitting device and the averagecolor of the output surface when viewed at an angle greater than 10degrees from the peak output angle is greater than 0.01 when emittinglight. In a further embodiment of this invention, the difference (Δu′v′)between the integrated light output color of a light emitting devicewhen emitting light and the average color of the output surface when thelight emitting device is not emitting light and is illuminated by astandard illuminant A when viewed at a first angle is greater than 0.01.In one embodiment of this invention, the light emitting device is asign, display, information device, or mirror which emits light of afirst color when turned on and the output surface has a second color (ormirrored look or information content) when turned off or viewed from asecond angle where the color difference (Δu′v′) between the first andsecond colors is greater than 0.01.

In a further embodiment of this invention, the view of the surface ofthe light emitting device comprising a light filtering directionalcontrol element has information bearing content such as graphics, text,icons, indicia, etc. In one embodiment, the information is visibleoutside of the illumination angles. In one embodiment, the lightabsorbing regions vary in absorption such that at least one of theambient reflected light or transmitted light exiting the light emittingdevice carries information in the form of text, graphics, icons or otherindicia. In one embodiment of this invention, the light emitting devicealso functions as a sign. In one embodiment of this invention, the lightemitting device is an exit sign wherein the sign can efficiently be readwhen the light source is off due to diffuse reflectance from the lightreflecting region. In one embodiment of this invention, a light emittingdevice comprises a lenticular lens array with a striped, printed, lightreflecting region and striped light transmitting clear region such thatthe light exiting the light transmitting region is refracted into asmaller angular range and the ambient light reflected displaysinformation content through reflection from the light reflectingregions. In a further embodiment of this invention, a light emittingdevice, light fixture, or light emitting sign comprises a lightabsorbing information region between a lenticular lens array and a lightreflecting region.

In one embodiment of this invention, a light filtering directionalcontrol element comprises a light absorbing region disposed between alenticular lens array and a light reflecting region such that theseparation between the light reflecting region and the light absorbingregion is greater than the thickness of the thinner of the two regions.By spatially separating the two regions, the angular output of the lightexiting the light filtering directional control element will have areduced angular width. By separating the light reflecting and lightabsorbing regions they form a parallax barrier which can be used tolimit the angular output without requiring a reduction in aperturewidth.

In a further embodiment of this invention, the focal point of thelenticules is substantially near at least one of the light absorbingregion or the light reflecting region. In a further embodiment, thefocal point is substantially in-between the light absorbing region andthe light reflecting region. By designing the substrate thickness,curvature and surface profile of the lenticules such that the focalpoint is located at the midpoint between the light reflecting and lightabsorbing regions, the light throughput is optimized due to the angularspread from the focal point to the light absorbing region being equal tothe angular spread from the focal point to the light reflecting region.

In a further embodiment of this invention, the light reflecting regionsand the light absorbing regions are in contact with each other such aswhite ink printed on a cured black ink or a black toner transferred ontoa white toner or a co-extruded polyester film with a black lightabsorbing layer and a white light reflecting layer.

LFDCE—Area Ratios

In one embodiment of this invention, the light filtering directionalcontrol element comprises at least one of light absorbing region withlight transmitting regions and a light reflecting region with lighttransmitting regions. The light transmitting aperture ratio, ART, is theratio of the surface area of the light transmitting region to the totalarea of either the light absorbing region or the light reflecting regionplus the area of the light transmitting region. This area ratio affectsthe total optical efficiency, angular output, the spatial color andluminance uniformity, and the angular color and illuminance uniformityof the light filtering directional control element or a light emittingdevice employing the same. For an element comprising a light reflectingregion, the light transmitting aperture ratio, ART is defined by theequation:

${AR}_{T} = \frac{A_{T}}{A_{R} + A_{T}}$

where AT is the area of the light transmitting region and AR is the areaof the light reflecting region. Similarly, for an element comprising alight absorbing region, the ratio of the surface areas is

${AR}_{T} = \frac{A_{T}}{A_{A} + A_{T}}$

where AT is the area of the light transmitting region and AA is the areaof the light absorbing region.

For linear lenticular lens arrays and linear light transmittingapertures, the ratio of the areas can also be determined by the ratio ofthe width of the light transmitting aperture to the pitch where thepitch is the width of the light transmitting region plus either thewidth of the light absorbing region or the light reflecting region.

Light filtering directional control elements having small lighttransmitting aperture ratios will output more collimated light (lightwith a smaller angular FWHM cross-section of the intensity) within theplane perpendicular to the output surface and parallel to the array thelenticular lenses (parallel to the plane comprising the refraction dueto the refractive lenses). Also, light filtering directional controlelements with small light transmitting aperture ratios may filter outmore spatial light intensity irregularities (non-uniformities such asblemishes) and when the element comprises a light reflecting region, therecycling will improve the spatial color and luminance uniformity andenable more thinner optical designs of light emitting devices.

In edge-lit light emitting devices, the light extracted near theincident edge is often much brighter than that at the far edge. Inedge-lit LED light fixtures, the same can be true and the regions of thelightguide corresponding to the regions between the LED's may lessbright than the regions closer to the LED's. The type, size, shape, andspatial arrangement of the light extraction features in edge-lit designsis typically adjusted to result in more uniform output from the lightemitting device. Recycling films such as 90 degree prism films,diffusers, light scattering films, and white reflective films aid theuniformity through recycling and scattering, however, for a given sizelight entrance edge, the fewer the LED's, the more difficult it is tocreate a spatially uniform light extraction profile.

A term that can be used to measure the distance required to mix andextract the light from the lightguide is the Luminance Mixing Distance(LMD). For light emitting devices, it is desirable to have a luminanceuniformity of at least 70%, or more preferably 80%. The sampledluminance uniformity is defined as 100%*(Lmin/(Lmax) where Lmin is theminimum measured luminance and Lmax is the maximum measured spotluminance. For use as a metric for the luminance mixing distance, theluminance uniformity is measured in the direction parallel to theentrance edge (typically parallel to the LED array) or in the directionperpendicular to the entrance edge. The LMD∥ is the distance measuredfrom the entrance edge of the lightguide to the point where the linearspatial luminance cross-section on the output surface of the lightemitting device along direction parallel to the entrance edge has aluminance uniformity of at least 80%. Secondary optics on the LED's oroptical components such as reflectors, lenticular lens arrays andanisotropic diffusers may be used on the entrance edge to reduce theLMD∥. The length in the plane parallel to the entrance edge of theincident light profile which is incident on the edge of a substantiallyplanar lightguide is termed Entrance Source Length (ESL). The EntranceSource Length is defined as the maximum spatial length on the entranceedge surface of a lightguide along a direction parallel to the edge ofthe lightguide enclosed by the angular FWHM of the intensity profile ofthe light incident on the edge. For light emitting devices with aconstant LED pitch and constant intensity profile incident on the edge,the ESL can be measured from the LED pitch, the angular intensityprofile from the LED (or LED plus secondary optics) and the distancefrom the LED (or LED plus secondary optics) to the edge of thelightguide. A larger ESL will have a higher luminance uniformity nearthe edge of the lightguide and thus the LMD∥ is reduced. In the case ofa multiple-LED edge-lit light emitting device, the larger the spacing orpitch (PL) between the LED's along one edge of a light emitting device,the larger the LMD∥ will be for a fixed optical system (same lightguideand optical components). As a result, one metric for describing theincident light profile on the edge of a lightguide in relationship toits affect on the uniformity is the Input Light Ratio, ILR, defined as

${ILR} = {\frac{ESL}{P_{L}}.}$

Light emitting devices with a small Input Light Ratio will require morelight recycling to achieve a fixed LMD∥ than a those with a high ILR. Incases where the LED's are spaced from the edge and the input profilesoverlap, the ILR ratio can be greater than 1. In the special case wherea single LED is used, the ILR is the ESL divided by the length of thedimension of the output surface substantially parallel to the entranceedge. In one embodiment of this invention, a light emitting device hasan ILR less than one selected from the group of 1, 0.7, 0.5, 0.3, 0.2and 0.1. In another embodiment of this invention, a light filteringdirectional control element comprises a lenticular lens array, a lightreflecting region, and a light transmitting region wherein the ILR isless than one selected from the group of 1, 0.7, 0.5, 0.3, 0.2 and 0.1.A metric for evaluating the effectiveness of a light emitting device tomix the light is the Source Adjusted Luminance Mixing Distance (LMD∥SA)which adjusts the LMD∥ by the Input Light Ratio and is defined asLMD_(∥SA)=LMD_(∥)×ILR.

A light emitting device with a high level of “fast mixing” (mixing thelight well over a short distance from the edge) has a very low LMD_(∥SA)and has a higher performance value. These high performance “fast mixing”light emitting devices have a small LMD_(II) and a small ILR value andthus a very small LMD_(∥SA). A light emitting device that has a largeLMD_(∥) and a small ILR or a small LMD_(∥) and a large ILR has anaverage performance and medium LMD_(∥SA) value. Light emitting deviceswith a large LMD_(II) and a large ILR high have a very large LMD_(∥SA)and poor mixing performance. In one embodiment of this invention, alight emitting device has a LMD_(∥SA) less than one selected from thegroup of 5 mm, 3 mm, 2 mm, and 1 mm. In another embodiment of thisinvention, a light filtering directional control element comprises alenticular lens array, a light reflecting region, and a lighttransmitting region wherein the LMD_(∥SA) is less than one selected fromthe group of 5 mm, 3 mm, 2 mm, and 1 mm.

The luminance of the light emitting device in the directionperpendicular to the input edge will typically be very high near theedge and fall-off the further the distance from the edge. The luminancemixing distance of a light emitting device in the directionperpendicular to the input edge, LMD⊥, is the distance measured along aline on the light emitting surface perpendicular to the entrance edge(passing through the midpoint of the light emitting surface in thedirection parallel to the edge) from the entrance edge of the lightguideto the closest point at which the luminance at any further point alongthe line is within 80% of the average of the remaining points along theline. In one example, if the LED array is on the left side of a lightemitting device, then the LMD⊥ is the distance from the edge of thelightguide to the first point along the middle of the light emittingdevice where all other points to the right are within 80% of the averageof the remaining points to the right. Secondary optics on the LED's oroptical components such as reflectors, lenticular lens arrays andanisotropic diffusers may be used on the entrance edge to reduce theLMD⊥. The length in the plane parallel to the entrance edge of theincident light profile which is incident on the edge of a substantiallyplanar lightguide is termed Entrance Source Length (ESL). The EntranceSource Length is defined as the maximum spatial length on the entranceedge along a direction parallel to the edge of the lightguide enclosedby the angular FWHM of the intensity profile of the light incident onthe edge. For light emitting devices with a constant LED pitch andconstant intensity profile incident on the edge, this can be measuredfrom the LED pitch, the angular intensity profile from the LED (or LEDplus secondary optics) and the distance from the LED (or LED plussecondary optics) to the edge of the lightguide. The location, size,spacing, shape, type, etc. of the light extraction features will have asignificant affect on the LMD⊥.

A light emitting device with a high level of “fast mixing” along adirection perpendicular to the LED array (mixing the light uniformlyacross the light emitting device) has a very high LMD⊥. In oneembodiment of this invention, a light emitting device has an LMD⊥ lessthan one selected from the group of 5 mm, 3 mm, 2 mm, and 1 mm. Inanother embodiment of this invention, a light filtering directionalcontrol element comprises a lenticular lens array, a light reflectingregion, and a light transmitting region wherein the LMD⊥ is less thanone selected from the group of 5 mm, 3 mm, 2 mm, and 1 mm.

As disclosed above in relation to luminance uniformity, one can alsomeasure the performance in terms of color uniformity. For coloruniformity, the Δu′v′ value is measured between all points in thedirection parallel to the entrance edge (typically parallel to the LEDarray) or in the direction perpendicular to the entrance edge. The ColorMixing Distance, CMD_(∥) is the distance measured from the entrance edgeof the lightguide to the point where the color uniformity Δu′v′ is lessthan 0.04 along a cross-section on the output surface of the lightemitting device along direction parallel to the entrance edge.Similarly, the Color Mixing Distance (Source Adjusted) is defined asCMD_(∥SA)=CMD_(∥)×ILR.

In one embodiment of this invention, a light emitting device has aCMD_(∥SA) is less than one selected from the group of 5 mm, 3 mm, 2 mm,and 1 mm.

In another embodiment of this invention, a light emitting devicecomprises a light filtering directional control element comprising alenticular lens array, a light reflecting region, and a lighttransmitting region wherein the CMD_(∥SA) is less than one selected fromthe group of 5 mm, 3 mm, 2 mm, and 1 mm.

In the direction perpendicular to the entrance edge, the Color MixingDistance, CMD⊥, is the distance measured along a line on the lightemitting surface perpendicular to the entrance edge (passing through themidpoint of the light emitting surface in the direction parallel to theedge) from the entrance edge of the lightguide to the closest point atwhich the color uniformity Δu′v′ at any point further point along theline is less than 0.1 from the remaining points along the line. In oneembodiment of this invention, a light emitting device has a CMD⊥ lessthan one selected from the group of 5 mm, 3 mm, 2 mm, and 1 mm. Inanother embodiment of this invention, a light filtering directionalcontrol element comprises a lenticular lens array, a light reflectingregion, and a light transmitting region wherein the CMD⊥ is less thanone selected from the group of 5 mm, 3 mm, 2 mm, and 1 mm.

LFDCE—Protective Layer

In one embodiment of this invention, a light filtering directionalcontrol element further comprises a protective layer to protect at leastone of the light reflecting or light absorbing region from beingscratched during assembly or operation. The protective layer may be alaminated PET layer adhered using a pressure sensitive adhesive, aprotective hardcoating such as those used in the projection screen andpolarizer industry or other protective layers or coatings known toincrease scratch resistance. In one embodiment of this invention, theprotective layer also provides the spacing between the lenticular lensarray and a light collimating element.

LFDCE—Alignment

In one embodiment of this invention, a light emitting device comprisestwo light filtering directional control elements wherein the lenticulesare arranged substantially orthogonal to each other. When a lightemitting device comprises a first light filtering directional controlelement on the output side of the light emitting device from a secondlight filtering directional control element wherein the lenticules arearranged substantially orthogonal to each other and the first lightfiltering directional control element comprises symmetrically diffusereflecting region, the reflected light will reflectively scatter in aplane parallel to the lenticules, which increases the angular FWHMoutput profile in that plane. In applications where highly collimatedlight emitting device output profiles in two orthogonal planes aredesired, this increase in the FWHM in a plane relative to the outputfrom the second light filtering directional control element isundesirable. In one embodiment of this invention, a light emittingdevice comprises a first light filtering directional control element onthe output side of the light emitting device from a second lightfiltering directional control element wherein the lenticules arearranged substantially orthogonal to each other and the first lightfiltering directional control element comprises an anisotropicallyreflecting region where the major axis of diffusion is oriented in aplane perpendicular to the lenticules of the first light filteringdirectional control element and the reflected light will reflectivelyscatter in a plane perpendicular to the lenticules and maintain thecollimation in the plane parallel to the lenticules.

Light Emitting Device Thickness

In one embodiment of this invention, the light emitting device is adirect-lit type. In another embodiment of this invention, the lightemitting device is an edge-lit type. Edge-lit light emitting devices cangenerally be made thinner than a direct-lit type or in some cases occupyless volume when a tapered lightguide is used. In one embodiment of thisinvention, the light filtering directional control element increases theuniformity, reduces the thickness and provides increased collimation. Inone embodiment of this invention, the light recycling and uniformityderived from the light reflecting region and the spatial filtering fromthe light transmitting region and lenticular lens array reduces thethickness of an edge-lit light emitting device. In one embodiment ofthis invention, a light emitting device comprises at least one LED lightsource, a lightguide, and a light filtering directional control elementand the distance between an outer surface of the lightguide and lightoutput surface of the light emitting device is less than one selectedfrom the group of 1.5 millimeters, 1 millimeter and 0.5 millimeters.

In one embodiment of this invention, a light emitting device comprises alight filtering directional control element and the thickness of thedevice, t, is less than 20 millimeters thick.

In a further embodiments, the thickness is less than 10 millimeters, 8millimeters or 5 millimeters. In one embodiment of this invention, thelight emitting device is a wall washing light fixture comprises a firstside disposed to be coupled to a wall. In a further embodiment, thedistance, L, along a line parallel to the first side from the lightemitting device output surface to the point of peak luminance is greaterthan 20 centimeters. In one embodiment, the thickness of the lightemitting device is less than 10 millimeters and the distance along theline parallel to the first side from the output surface to the point ofpeak illuminance is greater than 20 centimeters. In a furtherembodiment, d is equal to L.

The light filtering directional control element used in one embodimentof this invention enables the light to be directionally controlledtoward a specific off-axis positive far-field focal point and have apoint of peak illuminance relative to the output surface that results ina more uniform illuminance distribution upon a surface such as a wall atan angle to the output surface of the light emitting device. In oneembodiments of this invention, the light filtering directional controlelement permits the thickness of the light emitting device relative tothe width of the device to be reduced. In another embodiment of thisinvention, the thickness of the light emitting device comprising a lightfiltering directional control element. can be reduced relative to thedistance, L. In a further embodiment of this invention, the lightemitting device has a width, w, such that

$\frac{w}{t} > {5\mspace{14mu}{or}\mspace{14mu}\frac{w}{t}} > {10\mspace{14mu}{or}\mspace{14mu}\frac{w}{t}} > 20.$

In a further embodiment of this invention

$\frac{L}{t} > {5\mspace{14mu}{or}\mspace{14mu}\frac{L}{t}} > {10\mspace{14mu}{or}\mspace{14mu}\frac{L}{t}} > {20\mspace{14mu}{or}\mspace{14mu}\frac{L}{t}} > 50.$Other Films and Components

In one embodiment of this invention, a light emitting device comprises alight filtering directional control element which comprises a lenticularlens array, at least one of a light absorbing or light reflectingregion, and a lightguide designed to direct light along a direction suchthat the light can effectively be outcoupled from the lightguidespatially such that the uniformity of the light exiting the element isimproved when illuminated from the edge. In one embodiment of thisinvention, a light filtering directional control element comprises alenticular lens array optically coupled to at least one of a lightreflecting region with light transmitting apertures or a light absorbingregion with light transmitting apertures, where one region is opticallycoupled to a lightguide.

One or more elements or films within the light emitting device or lightfiltering directional control element may be combined by using adhesives(such as pressure sensitive adhesives), thermally bonding, co-extrusion,insert molding, and other techniques known to combine two polymericfilms or elements. In one embodiment of this invention, a lightfiltering directional control element, lenticular lens, or lightredirecting element comprises an element with surface relief structuresof a first material with a first refractive index ns that is at leastone of a lenticular lens array and light collimating element wherein theelement is physically coupled to second optical element by using secondmaterial with a second refractive index nc such that ns−nc>0.01. In thisembodiment, the lenticular lens or light redirecting element can bephysically coupled to another element while still retaining a level ofrefraction or reflection. In another embodiment, the value ns−nc isgreater than one selected from the group of 0.05, 0.1, 0.2, 0.4 or 0.5.In one embodiment of this invention, at least one of the lightguide, thelight filtering directional control element, the lenticular lens array,light redirecting element, or volumetric light scattering elementcomprises a high refractive index UV curable material such as known inthe optical film industry and described in U.S. Pat. Nos. 6,107,364,6,355,754, 6,359,170, 6,533,959, 6,541,591, 6,953,623 and internationalpatent application number PCT/GB2004/000667, the contents of each areincorporated by reference herein.

In one embodiment of this invention, a light emitting device comprises alight source, a lightguide and further comprises at least one additionalcoating or film selected from anti-reflection coating, anti-glarecoating, capping layers, capping layers designed to protect metalmetallic layers from oxidization or from other compounds such asadhesives, adhesives, glues, reflective films, tinted films, protectivefilms, graphic films, patterned films, tinted films, colored or tintedcoating, light scattering coating or film, hard coating or filmcomprising a hardcoating, housing element, decorative films, supportlenses, metallic support baskets, glass components, light transmittingcomponents, housing or element to hold more than one component together,element to enable rotation or translation of one or more elementsrelative to the other and other components known to be usable within alight fixture in the lighting industry and a backlight in the displayindustry or known to be usable in other light emitting devices.

In another embodiment of this invention a light emitting devicecomprises a lightguide and at least one additional collimating elementsuch as a 90 degree apex angle prismatic film. In one embodiment of thisinvention, pre-conditioning the light incident on the light filteringcollimating element, transmits more light and the FWHM angular outputangles of the light emitting device along one or more output planes isreduced relative to a light emitting device comprising just the lightrecycling directional control element. In one embodiment of thisinvention, a light emitting device comprises two crossed 90 degreeprismatic collimating films and a optical composite such that theangular width of the FWHM intensity profile within one output plane isless that 15 degrees. In a additional embodiment of this invention, alight emitting device comprises two crossed 90 degree prismaticcollimating films and a optical composite such that the angular width ofthe FWHM intensity profile within one output plane is less that 10degrees. In another embodiment of this invention, a light emittingdevice comprises two crossed 90 degree prismatic collimating films and aoptical composite such that the FWHM along one output plane is less than8 degrees. In another embodiment of this invention, a light emittingdevice comprises a light filtering collimating element, a first 90degree prismatic collimating film and a second 90 degree prismatic filmproviding brightness enhancement with anisotropic light scattering phasedomains dispersed within the substrate as describe in U.S. patentapplication Ser. No. 11/679,628, the contents of which is incorporatedherein by reference. In this embodiment, the angular width of the FWHMintensity profile within one output plane is less than one selected fromthe group of 8 degrees, 10 degrees, 15 degrees or 20 degrees. In anotherembodiment of this invention, a light emitting device comprises a 90degree prismatic collimating film disposed above an optical compositewherein the prisms are oriented substantially orthogonal to thelenticules and further comprises a second 90 degree prismatic filmdisposed on the opposite side of the optical composite providingbrightness and uniformity enhancement with anisotropic light scatteringphase domains dispersed within the substrate and a lightguide and atleast one light emitting diode. In one embodiment of this invention, theuse of at least one brightness enhancing or collimating film along witha optical composite which comprises a light absorbing region permitsmore light to pass through the optical composite due to the more highlycollimated incident light profile upon the light recycling directionalcontrol element. In one embodiment of this invention, a light emittingdevice comprises at least one collimating film selected from the groupof BEF, BEF II, BEF III, TBEF, BEF-RP, BEFII 90/24, BEF II 90/50,DBEF-MF1-650, DBEF-MF2-470, BEFRP2-RC, TBEF2 T 62i 90/24, TBEF2 M 65i90/24, NBEF, NBEF M, Thick RBEF, WBEF-520, WBEF-818, OLF-KR-1, and 3637TOLF Transport sold by 3M, PORTGRAM V7 sold by Dai Nippon Printing Co.,Ltd., LUMTHRU that sold by Sumitomo Chemical Co., Ltd. and ESTINAWAVEW518 and W425 DI sold by Sekisui Chemical Co., Ltd.

The light emitting device may also comprise an optical composite and alight re-directing component that re-directs a substantially portion ofthe light into an off-axis orientation. In one embodiment of thisinvention, a light emitting device comprises a optical composite and anon-symmetrical prismatic film such as a Image Directing Film (IDF orIDFII) or Transmissive Right Angle Film (TRAF or TRAFII) sold by 3M. Inone embodiment of this invention, a light emitting device comprises aoptical composite and a non-symmetrical prismatic film. In oneembodiment of this invention, a light emitting device comprises anoptical composite and a symmetrical prismatic film to re-distribute thelight symmetrically about an axis such as a prismatic film with a 60degree apex angle with the prisms oriented toward the output surface. Inother embodiment of this invention, a light emitting device comprises alenticular lens array, a light reflecting region, light transmittingregions, and a linear prism film with an apex angle between 45 degreesand 75 degrees where the substrate of the linear prism film is coupleddirectly or through another layer to the light reflecting regions withthe prisms oriented away from the lenticules. In another embodiment ofthis invention, the linear prism film is a “reverse prism film” such assold by Mitsubishi Rayon Co., Ltd. under the trade names of DIA ARTH150, H210, P150 and P210, or is a prismatic film of a similar type asdisclosed in the embodiments within U.S. Pat. Nos. 6,545,827, 6,151,169,6,746,130, and 5,126,882, the contents of which are incorporated byreference herein.

In one embodiment of this invention, a light emitting device comprisesan LED array on a flexible circuit disposed in a circular or arc shapein proximity to a lightguide within an optical composite or as aseparate component from the light recycling directional control element.In one embodiment of this invention, a light emitting device comprises acircular array of LED's on flexible circuit such that the light from theLED's is directed inward toward the center of a circular disc-shapedlightguide comprising light extraction elements of at least one typeselected from the group of embossed features, laser-ablated features,stamped features, inked surface patterns, injection molded features,etched surface patterns, sand or glass-blasted micro-patterns, uv curedembossing patterns, dispersed phase particle scattering, scattering fromregion comprising beads, fibers or light scattering or diffractingshapes or other surface relief pattern. In one embodiment of thisinvention, the light emitting device in the previous embodiment furthercomprises a light recycling directional control element. In thisembodiment, the light emitting device illuminates a circular display.

One or more elements or films within the light emitting device oroptical composite may be combined by using adhesives (such as pressuresensitive adhesives), thermally bonding, co-extrusion, insert molding,and other techniques known to combine two polymeric films or elements.In one embodiment of this invention, a optical composite comprises anelement with surface relief structures of a first material with a firstrefractive index n_(s) that is at least one of a lenticular lens arrayand light collimating element wherein the element is physically coupledto second optical element by using second material with a secondrefractive index n_(c) such that n_(s)−n_(c)>0.01. In this embodiment,the lenticular lens array or collimating element can be physicallycoupled to another element while still retaining a level of refractionor reflection. In another embodiment, the value n_(s)-n_(e) is greaterthan one selected from the group of 0.05, 0.1, 0.2, 0.4 or 0.5. In oneembodiment, the lenticular lens array or collimating element is made ofa high refractive index UV curable material (such as known in theoptical film industry and described in U.S. Pat. Nos. 6,107,364,6,355,754, 6,359,170, 6,533,959, 6,541,591, 6,953,623 and internationalpatent application PCT/GB2004/000667, the contents of each areincorporated by reference herein.

Light Transmitting Material Composition

In an embodiment of this invention, at least one of the lightguide,optical film or element, light scattering element, light redirectingoptical element, light filtering directional control element, lightscattering lens, protective lens, housing, mounting element, thermaltransfer element, volumetric light scattering element comprises a lighttransmitting material.

In one embodiment of this invention, the light transmitting material isa polymer or a polymer blend or alloy material comprising multiplepolymers, glass, rubbers, or other materials. Each material may be asingle phase or multiple phase material. In another embodiment of thisinvention, a light transmitting material is a material that transmitsover 5% of light between a wavelength range of 400 nm and 700 nm with arefractive index at the sodium wavelength of greater than 1.01.

Such polymers include, but are not limited to acrylics, styrenics,olefins, polycarbonates, polyesters, cellulosics, and the like. Specificexamples include poly(methyl methacrylate) and copolymers thereof,polystyrene and copolymers thereof, poly(styrene-co-acrylonitrile),polyethylene and copolymers thereof, polypropylene and copolymersthereof, poly(ethylene-propylene) copolymers, poly(vinyl acetate) andcopolymers thereof, poly(vinyl alcohol) and copolymers thereof,bisphenol-A polycarbonate and copolymers thereof, poly(ethyleneterephthalate) and copolymers thereof; poly(ethylene2,6-naphthalenedicarboxylate) and copolymers thereof, polyarylates,polyamide copolymers, poly(vinyl chloride), cellulose acetate, celluloseacetate butyrate, cellulose acetate propionate, polyetherimide andcopolymers thereof, polyethersulfone and copolymers thereof, polysulfoneand copolymers thereof, and polysiloxanes.

Numerous methacrylate and acrylate resins are suitable for one or morephases of the present invention. The methacrylates include but are notlimited to polymethacrylates such as poly(methyl methacrylate),poly(ethyl methacrylate), poly(propyl methacrylate), poly(butylmethacrylate), poly(isobutyl methacrylate), methylmethacrylate-methacrylic acid copolymer, methyl methacrylate-acrylatecopolymers, and methyl methacrylate-styrene copolymers (e.g., MSresins). Suitable methacrylic resins include poly(alkyl methacrylate)sand copolymers thereof. In particular embodiments, methacrylic resinsinclude poly(methyl methacrylate) and copolymers thereof. The acrylatesinclude but are not limited to poly(methyl acrylate), poly(ethylacrylate), and poly(butyl acrylate), and copolymers thereof.

A variety of styrenic resins are suitable for polymeric phases of thepresent invention. Such resins include vinyl aromatic polymers, such assyndiotactic polystyrene. Syndiotactic vinyl aromatic polymers useful inthe present invention include poly(styrene), poly(alkyl styrene)s,poly(aryl styrene)s, poly(styrene halide)s, poly(alkoxy styrene)s,poly(vinyl ester benzoate), poly(vinyl naphthalene), poly(vinylstyrene),and poly(acenaphthalene), as well as the hydrogenated polymers andmixtures or copolymers containing these structural units. Examples ofpoly(alkyl styrene)s include the isomers of the following: poly(methylstyrene), poly(ethyl styrene), poly(propyl styrene), and poly(butylstyrene). Examples of poly(aryl styrene)s include the isomers ofpoly(phenyl styrene). As for the poly(styrene halide)s, examples includethe isomers of the following: poly(chlorostyrene), poly(bromostyrene),and poly(fluorostyrene). Examples of poly(alkoxy styrene)s include theisomers of the following: poly(methoxy styrene) and poly(ethoxystyrene). Among these examples, suitable styrene resin polymers includepolystyrene, poly(p-methyl styrene), poly(m-methyl styrene),poly(p-tertiary butyl styrene), poly(p-chlorostyrene), poly(m-chlorostyrene), poly(p-fluoro styrene), and copolymers of styrene and p-methylstyrene. In particular embodiments, styrenic resins include polystyreneand copolymers thereof.

Particular polyester and copolyester resins are suitable for phases ofthe present invention. Such resins include poly(ethylene terephthalate)and copolymers thereof, poly(ethylene 2,6-naphthalenedicarboxylate) andcopolymers thereof, poly(1,4-cyclohexandimethylene terephthalate) andcopolymers thereof, and copolymers of poly(butylene terephthalate). Theacid component of the resin can comprise terephthalic acid, isophthalicacid, 2,6-naphthalenedicarboxylic acid or a mixture of said acids. Thepolyesters and copolyesters can be modified by minor amounts of otheracids or a mixture of acids (or equivalents esters) including, but notlimited to, phthalic acid, 4,4′-stilbene dicarboxylic acid,2,6-naphthalenedicarboxylic acid, oxalic acid, malonic acid, succinicacid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaicacid, sebacic acid, 1,12-dodecanedioic acid, dimethylmalonic acid,cis-1,4-cyclohexanedicarboxylic acid andtrans-1,4-cyclohexanedicarboxylic acid. The glycol component of theresin can comprise ethylene glycol, 1,4-cyclohexanedimethanol, butyleneglycol, or a mixture of said glycols. The copolyesters can also bemodified by minor amounts of other glycols or a mixture of glycolsincluding, but not limited to, 1,3-trimethylene glycol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol,1,9-nonanediol, 1,10-decanediol, 1,12-dodecanediol, neopentyl glycol,2,2,4,4-tetramethyl-1,3-cyclobutanediol, diethylene glycol, bisphenol Aand hydroquinone. Suitable polyester resins include copolyesters formedby the reaction of a mixture of terephthalic acid and isophthalic acidor their equivalent esters with a mixture of 1,4-cyclohexanedimethanoland ethylene glycol. In particular embodiments, the polyester resinsinclude copolyesters formed by the reaction of terephthalic acid or itsequivalent ester with a mixture of 1,4-cyclohexanedimethanol andethylene glycol.

Certain polycarbonate and copolycarbonate resins are suitable for phasesof the present invention. Polycarbonate resins are typically obtained byreacting a diphenol with a carbonate precursor by solutionpolymerization or melt polymerization. The diphenol is preferably2,2-bis(4-hydroxyphenyl)propane (so-called “bisphenol A”), but otherdiphenols may be used as part or all of the diphenol. Examples of theother diphenol include 1,1-bis(4-hydroxyphenyl)ethane,1,1-bis(4-hydroxyphenyl)cyclohexane,2,2-bis(4-hydroxy-3,5-dimethylphenyl-)propane,2,2-bis(4-hydroxy-3-methylphenyl)propane,bis(4-hydroxyphenyl)sulfideandbis(4-hydroxyphenyl)sulfone. Thepolycarbonate resin can be a resin which comprises bisphenol A in anamount of 50 mol % or more, particularly 70 mol % or more of the totalof all the diphenols. Examples of the carbonate precursor includephosgene, diphenyl carbonate, bischloroformates of the above diphenols,di-p-tolyl carbonate, phenyl-p-tolyl carbonate, di-p-chlorophenylcarbonate and dinaphthyl carbonate. Particularly suitable are phosgeneand diphenyl carbonate.

A number of poly(alkylene) polymers are suitable for phases of thepresent invention. Such polyalkylene polymers include polyethylene,polypropylene, polybutylene, polyisobutylene, poly(4-methyl)pentene),copolymers thereof, chlorinated variations thereof, and fluorinatedvariations thereof.

Particular cellulosic resins are suitable for phases of the presentinvention. Such resins include cellulose acetate, cellulose acetatebutyrate, cellulose acetate propionate, cellulose propionate, ethylcellulose, cellulose nitrate. Cellulosic resins including a variety ofplasticizers such as diethyl phthalate are also within the scope of thepresent invention.

Light Transmitting Material Additives

Additives, components, blends, coatings, treatments, layers or regionsmay be combined on or within the aforementioned regions to provideadditional properties to the light transmitting material. These may beinorganic or organic materials. They may be chosen to provide increasedrigidity to enable support of additional films or light emitting devicecomponents. They may be chosen to provide increased thermal resistanceso that the plate or film does not warp. They may be chosen to increasemoisture resistance, such that the plate does not warp or degrade otherproperties when exposed to high levels of humidity. These materials maybe designed to provide improved optical performance by reducing wet-outwhen in contact with other components in the light emitting device.Additives may be used to absorb ultra-violet radiation to increase lightresistance of the product. They may be chosen to increase, decrease, ormatch the scratch resistance of other components in the light fixture,display, backlight, or other light emitting device. They may be chosento decrease the surface or volumetric resistance of the element such asa lightguide or a region of the element to achieve anti-staticproperties.

The additives may be components of one or more layers of the opticalelement or lightguide. The additives may be coatings that are added ontoa surface or functional layers that are a combined during themanufacturing process. The additives may be dispersed throughout thevolume of a layer or coating or they could be applied to a surface.

Adhesives such as pressure-sensitive or UV-cured adhesives may also beused between one or more layers to achieve optical coupling. Materialsknown to those in the field of optical films, plates, diffuser plates,films and backlights to provide optical, thermal, mechanical,environmental, electrical and other benefits may be used in the volumeor on a surface, coating, or layer of the optical element or one of itsregions. The adhesive layer may also contain symmetric, asymmetric, or acombination of symmetric and asymmetric domains in order to achievedesired light-scattering properties within the diffusion layer.

Light Transmitting Material Anti-Static Additives

Anti-static monomers or inert additives may be added to one or moreregions or domains of the light transmitting material. Reactive andinert anti-static additives are well known and well enumerated in theliterature. High temperature quaternary amines or conductive polymersmay be used. As an anti-static agent, stearyl alcohol, behenyl alcohol,and other long-chain alkyl alcohols, glyceryl monostearate,pentaerythritol monostearate, and other fatty acid esters of polyhydricalcohols, etc., may be used. In particular embodiments, stearyl alcoholand behenyl alcohol are used.

Method of Manufacturing the Light Filtering Directional Control Element

In one embodiment of this invention, the light filtering directionalcontrol element is manufactured by according to a predetermined designby using traditional manufacturing techniques such as offsetlithography, web printing, letterpress, digital printing, and screenprinting used for lenticular graphics, prints, images and 3D displayssuch as known in the art. Methods of manufacturing lenticular prints aredisclosed in U.S. Pat. Nos. 7,136,185, 5,573,344, 5,560,799 and Ph.D.thesis by Gary Jacobsen for Dissertation Presented to the Faculty of theSchool of Engineering of Kennedy-Western University for the Degree ofDoctor of Philosophy in Engineering Management titled “FIRST NOVELINVENTION OF INLINE WEB FED ROLL PRINT MANUFACTURING PRODUCTION OFANIMATED/THREE DIMENSIONAL IMAGED PRINT PRODUCTS INCORPORATING ADVANCEDLENTICULAR TRANSPARENT SUBSTRATE . . . ITS ADVANTAGES AND THECOMPARISON/CONTRAST ORDER ANALYSIS TO PRIOR U.S.P.T.O. PATENTED ART.”,the contents of each are incorporated by reference herein. Typicallylenticular image prints comprise 2 or more images separated intoalternating strips disposed near the focal point of the lenticularlenses to generate two or more views in a stereoscopic or “flip” orother viewing mode. Similarly, light absorbing strips are printed,adhered, transferred or otherwise formed on the light input side oflenticular lens arrays in the projection screen and display industry.Methods for producing the light absorbing stripes or light absorbingregions within bead-based or lenticular screens are disclosed in U.S.Pat. Nos. 5,870,224, 6,307,675, 6,781,733, 6,829,086, 5,563,738,6,631,030, 5,563,738, 6,896,757, 6,912,089, 5,870,224 and 6,519,087, thecontents of each are incorporated by reference herein. Other methods ofobtaining light reflecting or light absorbing regions on a substrate orsubstantially planar surface of a lenticular lens array include thermaltransfer such as disclosed in U.S. Pat. No. 4,871,609, the contents ofwhich are disclosed herein by reference. The lenticular printmanufacturing or the projection screen manufacturing processes may bealtered or steps may be added to produce a light filtering directionalcontrol element comprised of a lenticular array or array of surfacerelief lenses such as beads, at least one of a light absorbing or lightreflecting region and a light transmitting region. In one embodiment ofthis invention, the light reflecting region is formed with a similarprocess to one of the methods in the aforementioned patents whereinlight absorbing particles such as carbon black are replaced with lightreflecting particles such as BaSO₄ or TiO₂. In one embodiment of thisinvention, a method of producing a light filtering directional controlelement comprises of forming a layer of light reflecting material on asubstrate, subsequently forming a layer of light absorbing material onthe light reflecting material, thermally or optically transferring thelight absorbing and light reflecting material in selected regions fromthe substrate to a substantially planar surface of a lenticular orsurface relief lens array film such that the light absorbing and lightreflecting regions are registered at a predetermined location on thesubstantially planar side of the lens array.

In another embodiment of this invention, a light filtering directionalcontrol element is produced by printing a light absorbing region upon alenticular lens array in a predetermined linear pattern in registrationwith the lenticules and subsequently printing a light reflecting regionin registration and on top of or spaced apart from the light absorbingregion. In another embodiment of this invention, a light filteringdirectional control element is produced by subsequently coating a lightabsorbing and light reflecting layer on lenticular substrate andsubsequently exposing through the lenticular lens array with infra-redillumination such that the light is focused in regions corresponding tothe focal point of the lenticular lenses such that at least one of thefollowing occur: the bond between the light absorbing region and thesubstrate is broken, the light absorbing material is ablated off of thesubstrate, the light absorbing material and the light reflectingmaterial is ablated off of the substrate. The light reflecting or lightabsorbing regions may comprise compositions such as infra-red absorbingdies, adhesion modifiers, light sensitive adhesion modifiers etc. suchthat the ablation occurs or the bond is broken at a sufficiently lowlaser power without significantly damaging the lenticular lens surfaceor the opposite, substantially planar surface. The IR exposure may befrom a frequency doubled-YAG laser, a CO₂ laser, a bank of collimatedinfra-red heating lamps or other IR light sources that can be collimatedthrough reflective or refractive optics or have a naturally low beamdivergence.

In a further embodiment of this invention, a method of producing a lightfiltering directional control element comprises forming a layer of lightreflecting material on a substrate, subsequently disposing a layer oflight absorbing material above the light reflecting material, depositingan array of spherical or substantially spherical beads of a diameterthat is at least twice as thick as the combined light reflective andlight absorbing regions, and applying pressure to the beads andsubstrate through the use of stamps, presses, rollers or films onrollers such that the beads are pressed into the light absorbing andlight reflecting regions, wherein one or more of the beads is insufficiently close proximity to the substrate to provide a lighttransmitting aperture. In a further embodiment of this invention, thelight transmitting aperture provided by the bead permits at least 20% ofthe incident light from the bead side to transmit through the lightfiltering directional control element. In a further embodiment of thisinvention, the method of manufacturing a light filtering directionalcontrol element further comprises and additional step of thermal,optical, evaporative, or radiation curing which substantially increasesthe bonding or substantially fixes the location of one or more of thebeads. In one embodiment of this invention, the exposed bead side of thelight filtering directional control element is further coated with asubstantially conformal (or low refractive index) protective sealant andcured (thermally, optically, evaporative, radiation, extrusion coated,etc) such that beads are substantially fixed in their location.

In a further embodiment of this invention, the light filteringdirectional control element is produced by optically coupling in one ormore regions a lenticular or bead-based surface refractive element to atleast one of a light absorbing and light reflecting region, and furtheroptically coupling the combined element to at least one of a lightcollimating film, a prismatic refractive or total internal reflectionbased film such as a “reverse prism” type film described in U.S. Pat.No. 5,126,882, the contents of which are incorporated by referenceherein, or IDF or TRAF manufactured by 3M, a symmetrically oranisotropically scattering volumetric or surface relief diffuser, or alightguide.

In a further embodiment of this invention, a method of producing a lightfiltering directional control element comprises forming a layer of lightreflecting material on a lenticular lens substrate or layer formedthereupon, exposing the light reflecting region with electromagneticradiation wherein the light reflecting layer is altered to form lighttransmitting regions in the areas of higher exposure by the process ofthe voided reflecting materials being heated to a temperature above it'sglass transition temperature and the voids collapse, thus increasing thetransmission in the region. In a further embodiment, heat is applied tothe light reflecting region before or during exposure such that thelight exposure required is reduced. Materials suitable to change theirtransmission due to collapsing voids due to heat or pressure aredescribed in U.S. patent application Ser. No. 10/984,390, the contentsof which are incorporated herein by reference. In a further embodimentof this invention the method of manufacturing a light filteringdirectional control element comprises the step of applying pressure to alenticular lens element with a light reflecting layer disposed on theopposite side or a layer thereupon of the lenticular lens element thanthe lenticules such that a sufficient amount of pressure is transferredto the voided light reflecting region to collapse one or more voidedregions disposed beneath the apex of the lenticules. In a furtherembodiment, the resulting light filtering optical element of theprevious embodiment has a light transmission greater than 20% in thecase of light entering the lenticule side as measured according to ASTMD1003. In a further embodiment, heat is applied to the lenticular lenselement during or before the application of the pressure in theaforementioned embodiment.

In a further embodiment of this invention, a method of producing a lightfiltering directional control element comprises forming or adhering amulti-layer polymeric reflector film on a lenticular lens substrate orlayer formed thereupon, exposing the multi-layer polymeric reflectorwith electromagnetic radiation wherein the light reflecting layer isaltered to form light transmitting regions in the areas of higherexposure. In this embodiment, the light reflecting regions may be mademore transmissive by the process of annealing (changing the refractiveindex in one or more directions in one or more layers or regions,ablation (removing one or more layers or regions), swelling or shrinking(expansion or shrinking in the thickness direction of one or more layersor regions such that the wavelengths corresponding to opticalinterference are shifted closer to the infra-red or UV wavelengthspectrum), or deforming (heating the region to a temperature above it'sglass transition temperature. Simultaneously applied pressure or heatingmay be used with one or more of the embodiments described herein formaking a light filtering directional control element so as to providethe benefit of at least one of increasing the transmittance in theregion, increasing production (or modification) speed, or enable themodification to occur with a lower light intensity such as providing abias temperature for melting or deforming.

In another embodiment of this invention, a method of manufacturing alight filtering directional control element comprises the steps ofcoating beads onto voided light reflecting film such as described hereinin the aforementioned voided film patents, applying heat and pressure tothe resulting film such that the beads penetrate into the lightreflecting film and collapse the voids and decrease the distance betweenthe opposite surface to the beads. In a further embodiment, theresulting light filtering optical element of the previous embodiment hasa light transmission greater than 20% in the case of light entering thelenticule side as measured according to ASTM D1003. By using glass beadsor beads made from cross-linked materials, the deformation temperaturecan be selected to be sufficiently greater than the voided material suchthat when pressure or pressure and heat are applied, the beads willdisplace the matrix material of the voided film and/or collapse thevoids in the voided material. In a further embodiment of this invention,the voided film used in the reflective region is one selected from thegroup of a biaxially oriented PET film, a biaxially orientedpolypropylene and a PTFE film.

In a further embodiment of this invention, the method of producing alight filtering directional control element comprises the step oftransferring a light reflecting region onto the substantially planarside of a lenticular lens sheet or layer thereupon by registering andlaser printing or using another electrostatic imaging process using awhite scattering toner such as produced by Automatic Transfer Inc or isdescribed in U.S. Pat. Nos. 4,855,204, 6,114,077, 6,921,617, and6,797,447, the contents of each are incorporated by reference herein.

In one embodiment of this invention, the process of producing a lightfiltering directional control element comprises the step of extrusionembossing (or UV cured embossing) onto or into a light scattering film alenticular or other lens pattern. In this embodiment, the thickness ofthe light filtering directional control element is reduced since thelight scattering film serves as a substrate of the lenticular lensarray. In designs where the light scattering region is disposed betweenthe lenticules and at least one of the light absorbing region and lightreflecting region, the total thickness of the light filteringdirectional control element is reduced. In one embodiment of thisinvention the process of producing a light filtering directional controlelement comprises extrusion embossing lenticular lens elements onto ananisotropic light scattering diffuser. The features maybe extrusionembossed into the light scattering film during the production of thelight scattering film or as a subsequent step where the features areembossed directly into a region of the light scattering film (includingcapping or outer regions of sufficient thickness) or a coating appliedto the surface of the light scattering film. In another embodiment ofthis invention, the process of producing a light filtering directionalcontrol element comprises the step of extrusion embossing (or UV curedembossing) onto or into a light scattering film a lenticular or otherlens pattern on one or both sides of a light scattering region or film.

In one embodiment of this invention, the process of producing a lightfiltering directional control element comprises the step of applying aUV sensitive material (such as Cromalin by DuPont) to the substantiallyplanar side of a lenticular lens or layer thereupon, exposing throughthe lenticules with substantially collimated UV light incidentsubstantially normal to the array of lenticules, applying lightabsorbing or reflecting particles or toner to the UV sensitive materialwhereupon the exposed regions are less tacky and the particles do notadhere to the UV sensitive materials in the region. In a furtherembodiment of this invention, the process of producing a light filteringdirectional control element comprises the step of applying a UVsensitive material to the substantially planar side of a lenticular lensor layer thereupon, exposing through the lenticules with substantiallycollimated UV light incident at an angle β₂ from a surface normal to thearray of lenticules, applying light absorbing or reflecting particles ortoner to the UV sensitive material whereupon the exposed regions areless tacky and the particles do not adhere to the UV sensitive materialsin the region. In one embodiment of this invention, P2 is greater thanone selected from the group of 5 degrees, 10 degrees, 20 degrees, 30degrees, and 45 degree. By exposing through the lenticules at an angle,the resulting spatial locations of the linear light transmitting regionsare displaced relative to UV exposure normal to the array of lenticulesand the resulting light filtering directional control element has anangular light output profile wherein the peak is at an angle β₃ from thenormal to the output surface where β₃>0 degrees such that the peakintensity of the output light is off-axis.

In a further embodiment of this invention, the method of producing alight filtering directional control element comprises the step of usinga white transfer pigment layer for the light reflecting region on alenticular lens film such as described in U.S. Pat. No. 5,705,315, thecontents of which are incorporated by reference herein. Other printingand transfer methods known in the printing industries may also be used.

Method of Manufacture of Lightguide or Optical Element

In one embodiment of this invention, at least one element or region of alightguide, light redirecting element, light scattering lens, lightscattering element, volumetric light scattering element, surface relieflight scattering element, light reflecting element, or reflector is anoptical composite comprising two or more regions of material comprisingat least one light transmitting material or light reflecting materialwith predetermined optical properties. In a further embodiment of thisinvention, a method of manufacturing at least one element or region of alightguide, light redirecting element, light scattering lens, lightscattering element, volumetric light scattering element, surface relieflight scattering element, light reflecting element, or reflectorcomprises at least one of the steps of extrusion, profile extrusion,casting, injection molding, stamping, embossing, thermoforming,laminating, welding, or other known polymer processing technique.Profile extrusion, thermoforming and injection molding are particularlyuseful methods for creating a curved lightguide or other element of thelight emitting device.

Optical Composite & Method of Manufacture

An optical composite comprises two or more regions of materialcomprising at least one light transmitting material or light reflectingmaterial with predetermined optical properties. The composite maycomprise two light transmitting materials wherein the optical propertiesmay be similar or substantially different. The composite may comprise alight transmitting material and a light reflecting metal material suchas a volumetric light scattering film optically coupled to an aluminumreflector. The optical composite may also comprise, for example, anon-scattering light transmitting material and a volumetric lightscattering material. In one embodiment of this invention, an opticalcomposite comprises two or more regions of material, comprising at leastone light transmitting material or light reflecting material withpredetermined optical properties, selected from a light transmittingmaterial, non-scattering light transmitting material, light redirectingelement, light scattering element, volumetric light scattering element,light reflecting element, metal-based light reflecting element,lenticular lens, light scattering lens, light filtering directionalcontrol element, tinted film, colored film, film with indicia, graphicsor text, or other film or component or combination presented in anembodiment of this invention or known in the field of lighting,backlighting for displays, or sign and graphics industry.

In one embodiment of this invention, a method of manufacturing anarticle comprises the steps of providing a mold for injection molding,providing a light source comprising a light emitting diode with a firstlight emitting source surface, providing a first volumetric lightscattering diffuser film comprising a first light scattering regioncomprising domains, placing the light source in a first predeterminedlocation and first angular orientation in the mold, placing the firstdiffuser film a in a second predetermined location, injecting a lighttransmitting thermoplastic material or light transmitting liquid polymerprecursor material into the mold such that the light transmittingmaterial is optically coupled to the diffuser film. In one embodiment ofthis invention, the article is an optical composite. In a furtherembodiment, the optical composite is a component of an illuminatingdevice light emitting device such as a light fixture or backlight for aliquid crystal display.

In one embodiment of this invention, an optical composite comprising avolumetric scattering region, a non-scattering region, and a lowrefractive index region is formed by extrusion laminating a volumetricscattering film with a low refractive index coating onto anon-scattering material. In this embodiment, the low refractive indexcoating is optically coupled onto the non-scattering region to form avolumetric scattering lightguide. The film with a low refractive indexcoating may be otherwise optically coupled to the non-scattering regionthrough adhesives, pressure sensitive adhesives and other methodsdiscussed herein. The low refractive index region may be directlyapplied to the non-scattering substrate and the volumetric scatteringregion may be disposed on the low refractive index region.

In another embodiment of this invention, an optical composite comprisinga volumetric scattering region, a non-scattering region, and a lowrefractive index region is formed by co-extruding three layerscomprising a low refractive index layer extruded in-between a volumetricscattering layer and a non-scattering layer. In a further embodiment ofthis invention, an optical composite comprising a volumetric scatteringregion, a non-scattering region, and a low refractive index region isformed by co-extruding two layers comprising a low refractive indexmatrix material with dispersed phase domains onto a non-scatteringlayer. Other variations in include the order of the extrusion layers anda first layer or composite is extruded onto a second layer or compositeand are included within the scope of this invention.

In another embodiment of this invention, an optical composite comprisinga volumetric scattering region, a non-scattering region, and a lowrefractive index region is formed by injection molding a non-scatteringmaterial into a mold which comprises a volumetric light scattering filmwith a low refractive index coating. In another embodiment of thisinvention, one or more layers corresponding to a non-scattering region,volumetric scattering region, or low refractive index region aresequentially or simultaneously molded into one or more molds with orwithout an article previously positioned in the mold using a 1-shot,2-shot or 3-shot injection molding process.

In another embodiment of this invention, the method of manufacturing anoptical composite comprising a low refractive index region comprises atleast two methods selected from the group of extrusion, injectionmolding, lamination, coating, bonding, thermal or light sensitiveadhesive bonding, thermosetting, thermoforming, vacuum thermoforming,mechanical and optical coupling, ultrasonic welding, laser welding, andother methods known in the polymer or polymer film industry for joiningtwo materials or layers together or forming or coating one layer ormaterial upon another.

In a further embodiment of this invention, the method of manufacturingan article further comprises positioning the light source such that thelight transmitting material is optically coupled to the output surfaceof the light source. In one embodiment of this invention, the moldcomprises a patterned surface with light extracting surface featuresdisposed thereon.

In a further embodiment of this invention, the anisotropic lightscattering film comprises a surface with light redirecting surfacefeatures such as light collimating surface features or light extractingsurface features. In one embodiment of this invention, the method ofmanufacturing an article further comprises orienting the anisotropiclight scattering diffuser film containing asymmetric domains such thatthe asymmetric domains are aligned with their longer dimensionsubstantially parallel to the first optical axis of the first lightsource.

In a further embodiment, the light source comprises an array of lightemitting diodes with a first light source optical axis. In oneembodiment of this invention, the anisotropic diffuser film is orientedin the mold with its asymmetric domains substantially aligned parallelto the optical axis of the light source.

A further embodiment of this invention includes aligning the lightsource such that its optical axis is substantially parallel to the firstlight output surface and the volumetric anisotropic light scatteringfilm is oriented in the mold with the asymmetric domains aligned withtheir longer dimension substantially parallel to the first optical axisof the first light source. A further embodiment of this inventionincludes aligning the asymmetric film with the asymmetric domainsaligned with their longer dimension substantially perpendicular to thefirst light source array axis.

In a further embodiment of this invention, the volumetric anisotropiclight scattering diffuser film has an anisotropic ratio, AR, defined bythe ratio of the first angular width at half maximum diffusion intensityin a plane perpendicular to the first light source axis of FWHM₁ and asecond angular width at half maximum diffusion intensity in a planeparallel to the first light source axis of FWHM₂ such that AR>2, orpreferably AR>5, or more preferably AR>10. In this embodiment, thescattering in the output surface plane is minimized by having a high DARratio such that the output coupling can be controlled by the lightextraction features.

In a further embodiment of this invention, the volumetric anisotropiclight scattering diffuser film has a domain asymmetry ratio, DAR,defined by the ratio of the first average dimensional length in a planeperpendicular to the first light source axis of L₁ to a second averagedimensional length in a plane parallel to the first light source axis ofL₂ where DAR>2, DAR>5, or DAR>10. In this embodiment, the scattering inthe output surface plane is minimized by having a high DAR ratio suchthat the output coupling can be controlled by the light extractionfeatures.

In a further embodiment of this invention, a volumetric scatteringregion is disposed substantially beneath the light emitting diode outputsurface relative to the light output surface. In one embodiment, thevolumetric anisotropic light scattering film is disposed to receivelight directly from a point on the light emitting source surface at anincidence angle in the light transmitting material of less than 20degrees from a normal to the first light output surface. In a furtherembodiment, the anisotropic light scattering film is disposed to receivelight directly from the light source output surface at an incidenceangle in the light transmitting material parallel to the normal to thefirst output surface.

In one embodiment of this invention, the light source is positioned suchthat the optical axis passes through a non-scattering region of thevolumetric scattering lightguide or volumetric scattering region. In afurther embodiment of this invention, the volumetric scattering regioncomprises a second light scattering region separated from the firstlight scattering region by a substantially non-scattering region.

In one embodiment of this invention the method of manufacturing anarticle further includes the step of placing a second volumetricanisotropic light scattering diffuser film comprising asymmetricallyshaped domains in a third predetermined location and third angularorientation in the mold before injecting material into the mold.

In a further embodiment of this invention, the mold further comprises alight collimating feature disposed to reduce the angular extent of thelight incident on the light redirecting features within the lighttransmitting material within a plane perpendicular to the first outputsurface and parallel to the light emitting device optical axis.

In one embodiment of this invention, the light transmitting materialcomprises substantially spherical light scattering domains. In oneembodiment, the substantially spherical light scattering domains alongwith a tapered light transmitting material function together byscattering and reflecting to create a substantially uniform spatialluminance along the first output surface in a direction perpendicular tothe light source array axis.

In one embodiment of this invention, a volumetric scattering lightguidecomprises a diffuser film with a first diffuser surface in opticalcontact with the light transmitting material wherein the first diffusersurface substantially comprises a first diffuser film material with amelt temperature T_(m1) and the light transmitting material has a secondmelt temperature T_(m2) such that T_(m1)−T_(m2)>20 degrees Celsius. Inanother embodiment of this invention, T_(m1)−T_(m2) is greater than 40degrees Celsius. In a further embodiment, T_(m1)−T_(m2) is greater than60 degrees Celsius.

In one embodiment of this invention, a lightguide is formed from lighttotally internally reflecting from a surface of one or more of the firstlight transmitting materials, non-scattering region, volumetricscattering region, light extracting region, surface relief featureregion, light reflecting element, second light transmitting material,light diffusing film, light redirecting optical film, or other opticalcomponent optically coupled to the light transmitting material ornon-scattering region.

Insert molding and extrusion lamination are two examples of secondaryprocesses that can be used to achieve a thickness of an opticalcomponent or composite of greater than 1 mm. One embodiment of thisinvention is volumetric scattering lightguide composite comprising avolumetric scattering region of less than 1 mm in thickness and a secondsubstantially light transmitting non-scattering region that is greaterthan 1 mm in thickness. In a further embodiment, the non-scatteringregion is substantially transparent to light in the visible wavelengthspectrum. In a further embodiment, the composite has light redirectingfeatures within the volume or on the surface of the light transmittingregion. Light redirecting features include refractive, reflective orscattering features such a lenses, prisms, hemispherical, definedoptical shapes with functionality, or arrays or patterns of thesefeatures. Examples of light redirecting features, layers configurations,additives, material selections, applications, light sources, opticalproperties and methods of component manufacturing are described in U.S.patent application Ser. Nos. 11/679,628, 11/223,660, 11/282,551,11/426,198, and 60/820,241, the entirety of each are incorporated hereinby reference. The mold tool or roller may include a light redirectingfeature or the film inserted may contain the light redirecting feature.

In one embodiment, the extrusion lamination, injection molding, or othermaterial used in a secondary process contains dispersed domains. Thesedomains may be asymmetrically shaped, symmetrically shaped, orientedalong at least one axis. In one embodiment, these domains comprise atleast one of an immiscible polymer, cross-linked particles, glassmicrospheres, hollow glass microspheres, polymer fibers, inorganicfibers, glass fibers, dispersed polymer beads, particles, core-shellparticles, and other materials and additives known to be usable inoptical components. In one embodiment of this invention, the opticalcomposite comprises polymer photonic crystal fiber (PCF) such asdisclosed in U.S. patent application Ser. No. 11/067,848, the entiretyof the application is incorporated herein by reference. In anotherembodiment of this invention, the optical composite includes fiberscomprising co-continuous phases such as disclosed in U.S. patentapplication Ser. No. 11/068,313, the entirety of the application isincorporated herein by reference. In one embodiment of this invention,the optical composite comprises composite polymer fibers such as thosedisclosed in U.S. patent application Ser. No. 11/068,158, the entiretyof the application is incorporated herein by reference. In a furtherembodiment of this invention, the optical composite comprises inorganicfibers such as those disclosed in U.S. patent application Ser. No.11/125,581, the entirety of the application is incorporated herein byreference. In a further embodiment of this invention, the opticalcomposite comprises a polymer weave such as described in U.S. patentapplication Ser. No. 11/068,590, the entirety of the application isincorporated herein by reference.

In one embodiment of this invention, the optical composite may provideone or more of the following optical functions: absorptive polarizer,reflective polarizer, scattering polarizer, substantially symmetricallyscattering diffuser, anisotropically scattering diffuser, forwardscattering diffuser, backward scattering diffuser, collimating element,light redirecting element, refracting element, spatial lighthomogenizer, increased axial luminance, increased spatial luminanceuniformity along at least one axis, reduced speckle from coherentsources, non-depolarizing transmission, non-depolarizing reflection,increased angular luminance uniformity, increased forward speculartransmission.

In one embodiment of this invention, substantially matching therefractive index of the optical film continuous phase material with thelight transmitting material increases the optical efficiency due to thereflection intensity reduction from the interface. In one embodiment,the refractive index of the continuous phase material substantiallymatches the refractive index of the light transmitting region along atleast one axis. In one embodiment, the difference between the refractiveindex of the optical film continuous phase material and the lighttransmitting material along a first axis is less than 0.05.

In one embodiment of this invention, the optical composite creates animproved light guide. The optical composite can include more than onelight scattering region that is co-extruded or co-laminated or extrusionlaminated on one or more sides of the component. In one embodiment anenhanced optical component comprises an anisotropic light scatteringcomponent on one side of a thicker, substantially non-scattering regionwith at least one additional light scattering region optically coupledto the non-scattering region. In a further embodiment, two anisotropiclight scattering films are optically coupled to a thicker substantiallynon-scattering region. This can be achieved by insert molding two filmsor extrusion laminating on a sheet with two film feeds. In a furtherembodiment, a light scattering component comprising a polycarbonatecontinuous phase region is optically coupled to polystyrene region byextrusion laminating to the polystyrene sheet during the extrusionprocess. An adhesive promoter or adhesive such as a compatibilizer maybe used. In this example, the refractive indexes of the polycarbonateand polystyrene are substantially indexed matched along a first axis. Inthis example, the composite has an increased shatter resistance over thepolystyrene due to the polycarbonate matrix film bonded to thepolystyrene. In a further embodiment, two anisotropic light scatteringfilms are insert-molded on opposite sides of a PMMA region.

In one embodiment, of this invention, a lightguide composite comprises asubstantially non-scattering light transmitting material (or a materialwith a Clarity greater than 50%) and dispersed phase domains wherein thecomposite is manufactured by injection molding the non-scattering lighttransmitting material into a mold comprising a volumetric lightscattering film. In another embodiment, of this invention, an arcuatelightguide composite comprises a substantially non-scattering lighttransmitting material (or a material with a Clarity greater than 50%)and dispersed phase domains wherein the composite is manufactured byinjection molding the non-scattering light transmitting material and alight scattering material comprising dispersed phase domains into a moldusing a two-shot process.

In one embodiment, of this invention, a lightguide composite comprises asubstantially non-scattering light transmitting material (or a materialwith a Clarity greater than 50%) and light extraction features whereinthe composite is manufactured by injection molding the non-scatteringlight transmitting material into a mold comprising a film with lightextraction surface features. In another embodiment, of this invention,an arcuate lightguide composite comprises a substantially non-scatteringlight transmitting material (or a material with a Clarity greater than50%), dispersed phase domains, and light extraction features wherein thecomposite is manufactured by injection molding the non-scattering lighttransmitting material and a light scattering material comprisingdispersed phase domains into a mold with inverted light extractionfeatures using a two-shot process.

In one embodiment, the light guide comprises a volumetric scatteringregion on opposite sides of a substantially non-scattering region. In atypical light guide, a portion of the light traveling along the lightguide is totally internally reflected from the lightguide-air interface.At least one additional lightguide is created when a component has ananisotropic light scattering region on one or both sides of thenon-scattering region. A portion of the light incident on the lightscattering region will scatter, reflect, or diffract off of one or moredisperse phase domain-matrix interfaces and continue to travel along thelight guide. A portion of the light that passes through the lightscattering region will be scattered out of the light guide and a secondportion of the light will totally internally reflect off of thematrix-air interface. In this embodiment, the matrix-air interface formsan outer lightguide and the two substantially parallel light scatteringregions form an inner light guide. Each light scattering region alsoforms a lightguide with each surface. The anisotropic light scatteringregions may be oriented orthogonally to each other. The light scatteringregions may be polarization dependent, polarization independent,wavelength dependent, or a spatially varying combination thereof and thenon-scattering regions may be birefringent, tri-refringent,substantially isotropic, or a spatially varying combination thereof.

In a further embodiment of this invention, two substantially planarlight scattering regions are oriented at an angle θ5 with respect toeach other with a substantially non-scattering region optically coupledand disposed in an optical path between the two regions. In oneembodiment, substantially planar anisotropic light scattering regionsare oriented 90° to each other on the edge and face of a non-scatteringlight guide. In a further embodiment, the thickness of at least one ofthe light scattering regions is less than 1 millimeter and the thicknessof the substantially non-scattering region is greater than onemillimeter. In a further embodiment, the thickness of at least one ofthe light scattering regions is less than 0.5 millimeter and thethickness of the substantially non-scattering region is greater than 0.5millimeters. In a further embodiment, the thickness of at least one ofthe light scattering regions is less than 0.5 millimeter and thethickness of the substantially non-scattering region is greater than 1millimeter. In a further embodiment the thickness of the non-scatteringlight region is at least twice the thickness of at least one of thelight scattering regions. This allows the light scattering propertieswhich can be better controlled through a film extrusion process to beutilized in an injection molded or thick extrusion process wherein it isdifficult to achieve the desired optical properties and orientation ofthe thicker, extruded material.

The improved optical composite of this invention can be used to provideimproved luminance uniformity and angular light distribution whenilluminated from the edge. The optical composite of this invention canbe used as a light guide for illuminating a spatial light modulatingdevice such as an LCD. In one embodiment, the optical compositeilluminates an LCD providing spatial luminance uniformity. The lightemitting device or optical composite may comprise one or more lightre-directing, brightness enhancement, prismatic films, reflective orabsorptive polarizers, non-polarization dependent light homogenizer,polarization-dependent light homogenizer, or other optical filmscommonly used in backlights for displays may also be used to provideimproved light efficiency, re-direction, or recycling. Polarizationsensitive light homogenizers such as those discussed in U.S. patentapplication Ser. No. 11/828,172, the contents of which are incorporatedby reference herein, may be used as the anisotropic light scatteringfilm, an additional film within the optical composite or in conjunctionwith the optical composite to form a light emitting device, backlight orlight fixture. One or more of the anisotropic light scattering films orregions disclosed herein may be a high clarity scattering layer such asthose described in U.S. patent application Ser. No. 11/958,361, thecontents of which are incorporated by reference herein. Multi-functionalnon-imaging optical components such as those discussed in U.S. patentapplication Ser. No. 12/030,203, the contents of which are incorporatedby reference herein, may be used as the anisotropic light scatteringfilm, an additional film within the optical composite or in conjunctionwith the optical composite to form a light emitting device, backlight,or light fixture. In addition to the light redirecting films disclosedherein, light redirecting elements such as those discussed in U.S.patent application No. 60/985,649, the contents of which areincorporated by reference herein, may be used as the anisotropic lightscattering film, an additional film within the optical composite or inconjunction with the optical composite to form a light emitting device,backlight, or light fixture. The optical composite in accordance withone embodiment of this invention further comprises a light filteringcollimating element such as described in an embodiment of U.S. patentapplication No. 61/028,905, the contents of which are incorporated byreference herein. The optical composite in accordance with anotherembodiment of this invention further comprises a optical composite suchas described in an embodiment of U.S. patent application No. 61/036,062,the contents of which are incorporated by reference herein.

In a further embodiment of this invention polarization sensitive opticalfilms are insert-molded one on or more sides of a light guide to provideincreased optical efficiency through polarization recycling. These filmsmay be specularly reflecting or provide anisotropic scattering that ispolarization sensitive. In a further embodiment of this invention, theoptical composite comprises at least one polarization sensitive lighthomogenizer to provide improved spatial luminance uniformity, lightrecycling efficiency for a pre-determined polarization state or improvedangular redirection of light.

The optical composite of this invention may be used to increase theluminance uniformity or angular light distribution of a light emittingdevice such as a light fixture, information display, or illuminator.

In a further embodiment of this invention, the composite comprises ananisotropic light scattering region and a surface relief structureformed within the volume of the substantially non-scattering region. Thesurface relief structure can provide additional light redirection,collimation, extraction, diffusion, recycling or other desired opticalfunctionality such as those commonly used with backlights for LCD's. Thesurface relief structure may be located on more than one surface of thecomposite. In one embodiment, the surface relief profile is machinedinto the tool of the mold used in the insert molding process. In afurther embodiment a casting roll is milled to provide the desiredsurface structure on one side of the composite with an optical filmextrusion laminated to the opposite side.

In a further embodiment of this invention, an enhanced optical compositecomprises an anisotropic light scattering region, a substantiallynon-scattering region and an optically coupled light emitting sourcesuch as an LED. In one embodiment of this invention, one or more LED'sor arrays of LED's are insert molded along with an anisotropic lightscattering region to form a light emitting optical composite. In oneembodiment, the anisotropic light scattering region forms a secondarylight guide to provide increased luminance uniformity. Other methods forcombining light sources to a light guide are described in U.S. patentapplication Ser. No. 11/494,349 the entirety of which is incorporatedherein by reference.

In one embodiment of this invention, a linear array of LED's isoptically coupled along with a light scattering film in an extrusionlamination process to a substantially non-scattering region that isthicker than the light scattering region. In a further embodiment, thelinear array of LED's are formed with high temperature materials suchthat the melting temperature of the LED materials is higher than that ofthe molten extrusion material. In a further embodiment, the LED array iscooled below ambient temperature in the extrusion process such that theheat from the molten polymer is dissipated through the LED materialsbefore causing damage.

In one embodiment of this invention, a light emitting device comprisesan optical composite and a light emitting source where in the opticalcomposite comprises a substantially non-scattering region of a firstthickness, d1, and at least one anisotropic light scattering region of asecond thickness, d2, optically coupled to the non-scattering regionwherein a portion of the light from the light emitting source isanisotropically scattered from the anisotropic light scattering region,passes through the non-scattering region and totally internally reflectsfrom the air-non-scattering region interface such that upon scatteringfrom the light scattering region upon the second pass it is scattered toan angle that is less than the critical angle of the air-non-scatteringregion interface, escapes the composite and the spatial luminanceuniformity is greater than 70%. In a further embodiment, d1 is greaterthan d2 or d1>2*d2 or d1>4*d2 or d1>6*d2. In a further embodiment, atleast 5% percent of the light incident normal to the surface of thecomposite passes through the anisotropic light scattering region atleast twice. In a further embodiment, at least 20% percent of the lightincident normal to the surface of the composite passes through theanisotropic light scattering region at least twice. In a furtherembodiment, at least 50% percent of the light incident normal to thesurface of the composite passes through the anisotropic light scatteringregion at least twice.

In a further embodiment, the anisotropic light scattering regioncontains asymmetrically shaped domains oriented substantially parallelto a linear array of LEDs or an array of linear fluorescent bulbs. Bytransferring the total internal reflection interface to an interfacelocated at a distance further from the light source, the light guidecreated by the scattering region and the TIR surface will improve thespatial luminance uniformity.

Method of Manufacture—Injection Molding Process

In one embodiment, of this invention, an arcuate lightguide comprises asubstantially non-scattering light transmitting material (or a materialwith a Clarity greater than 80%) and light extraction features whereinthe composite is manufactured by injection molding the non-scatteringlight transmitting material into a mold comprising inverted lightextraction surface features. Methods, techniques, and materials suitablefor injection molding of optical components and optical films are knownin the art and include those referenced in U.S. Pat. Nos. 7,270,465 byKeh et al, 6,490,093 by Guest, and U.S. patent application Ser. No.11/273,863, the entire contents of each are incorporated herein byreference. In one embodiment of this invention, the method ofmanufacturing the lightguide, light redirecting element, scatteringelement or optical composite is a 2-shot injection molding process. Inone embodiment, a first light transmitting material of a melttemperature T_(m3) is injection molded into a mold comprising the lightsource. In a second step, a surface of the mold is removed and a secondlight transmitting material of a melt temperature T_(m4) is injectedinto the mold such that the first light transmitting material isoptically coupled to the second light transmitting material andTm3−T_(m4) is greater than 20 degrees Celsius. In a further embodimentof this invention, T_(m3)−T_(m4) is greater than 40 degrees Celsius. Inanother embodiment, T_(m3)−T_(m4) is greater than 60 degrees Celsius. Inone embodiment of this invention, the light transmitting materialcomprising the at least one of the light redirection features or lightdiffusing film is protected from thermal damage during operation of thelight emitting device by a thermal buffer material of a second lighttransmitting material with a higher melt temperature that is opticallycoupled and bonded to the first light transmitting material. In oneembodiment, a high temperature material such as a polycarbonate orfluoropolymer can be injection molded and optically coupled to the LEDlight emitting surface and material with a lower injection moldingtemperature such as PMMA can be used to generate the light redirectingfeatures or optically couple to the light diffusing film such that thefilm does not melt nor need to be made of a high temperature material.By being able to optically couple a first light transmitting material tothe light source emitting surface less light more light is transmittedsince there isn't a material-air interface upon which light willreflect.

Optical Efficiency of Light Emitting Device

In one embodiment of this invention, the optical efficiency of the lightemitting device is greater than one selected from the group of 50%, 60%,70%, 80%, 90% and 95%. One may improve the optical efficiency of thelight emitting device or component by using material with very lowinternal visible light absorption. The optical efficiency of the lightemitting device is determined by all of the optical components of thesystem. All materials used in optical devices absorb at least a verysmall amount of light. With this in mind, one may design a system with areduced number of reflections, however, the absorption from somematerials is greater than others and there are often other systemtradeoffs to make in order to achieve goals such as form factor(edge-lit designs) and output surfaces with luminance micro-uniformitiesor macro-uniformities greater than 70%. A total internal reflection in ahighly transparent material is often more efficient than a reflectionfrom a coated surface or a voided film. In one embodiment of thisinvention, a volumetric scattering lightguide comprises a low refractiveindex region disposed in-between and optically connecting anon-scattering region and a volumetric scattering region which totallyinternally reflects light from an angular range in the non-scatteringregion greater than 80 degrees from the surface normal and the opticalefficiency light emitting device or volumetric scattering region isgreater than one selected from the group of 50%, 60%, 70%, 80%, 90% and95%.

Luminance Uniformity of Light Emitting Device

In one embodiment of this invention, a lightguide comprises a lowrefractive index region disposed between light extracting region and anon-scattering region and the luminance macro-uniformity or luminancemicro-uniformity of at least one light output surface is greater thanone selected from the group of 50%, 60%, 70%, 80%, 90% and 95%. Inanother embodiment of this invention, the light emitting device has aluminance macro-uniformity or luminance micro-uniformity of at least onelight output surface greater than one selected from the group of 50%,60%, 70%, 80%, 90% and 95%.

The luminance macro-uniformity is a metric for measuring the luminanceover the light emitting surface looking at large regions. The sampledluminance uniformity is defined as 100%*(Lmin/Lmax) where Lmin is theminimum measured spot luminance and Lmax is the maximum measured spotluminance. As used herein, the luminance macro-uniformity is the sampledspatial luminance uniformity measured over a contiguous light outputsurface of the light emitting device with a 9 spot sampled luminanceuniformity measurement according to VESA Flat Panel Display MeasurementStandard version 2, section 306.1.

The luminance micro-uniformity is a metric for measuring the spatialluminance uniformity in a sub-region (such as the region near the lightsource) of the light emitting surface. As used herein, the luminancemicro-uniformity is the sampled spatial luminance uniformity measured inthe sub-region of the light output surface of the light emitting devicewith a 9 spot sampled luminance uniformity measurement according to theVESA Flat Panel Display Measurement Standard version 2, section 306.1where the sub-region area defines the measurement boundaries, thecontents are incorporated by reference herein.

The use of a low refractive index region can increase the luminancemacro-uniformity and the micro-uniformity. In one embodiment of thisinvention, the spatial luminance micro-uniformity of the sub-regionnearest the light source of the light output surface is greater than oneselected from the group of 50%, 60%, 70%, 80%, 90% and 95%. In a furtherembodiment of this invention, the sub-region nearest the light source isthe region of the light output surface nearest the light source,centered in the light output surface area in the direction orthogonal tothe light source optical axis wherein the area of the measuredsub-region is square and the equal dimensions of the area are a multipleof the lightguide thickness selected from the group of 1, 2, 5, 10, and20. For example, the sub-region of a lightguide with a thickness of 5millimeters may be a sub-region of the light output surface near thelight source, centered in the direction orthogonal to the optical axisof the light source with a multiple of 10 and dimensions of 50millimeters by 50 millimeters.

Light Output Profile of Light Emitting Device

In one embodiment of this invention, a light emitting device has a peakangle of illuminance greater than 0 degrees from the normal to the lightoutput surface. In a further embodiment of this invention, a lightemitting device has a light output profile resembling a batwing profilewith peak angles greater than 50 degrees from the normal to the lightoutput surface. In another embodiment of this invention, a lightemitting device has more than one peak luminescent intensity profile. Inanother embodiment of this invention, the light output profile of thelight emitting device has an angular luminescent peak intensity whereinthe peak is at an angle β₃ from the normal to the light output surfacewhere β₃>0 degrees such that the peak intensity of the output light isoff-axis.

In a further embodiment of this invention, a light emitting device has aluminous intensity output profile that is symmetric in a first outputplane about the light emitting device optical axis and asymmetric in asecond plane orthogonal to the first, wherein the optical axis of thelight emitting device is the central angle of symmetry in the firstplane and the angle of peak luminous intensity in the second plane.

In a further embodiment of this invention, the angular luminescentintensity output of the light emitting device varies in differentsurface regions of the light emitting output surface. The angular lightoutput profile may vary spatially by increasing the aperture width insome regions and reducing the aperture width along at least one axis inorder to provide a light emitting device with a precisely tailoredoutput profile. In one embodiment of this invention, the angular outputin different spatial regions is varied by adjusting the locations of theapertures or light transmitting regions in a first direction in a firstplane relative to the optical axes of the corresponding lenticularelements where the first plane is perpendicular to the optical axes.

In another embodiment of this invention, the light emitting device has afocusing or concentrating light output profile. By adjusting thedifferent properties of one or more regions spatially, the light fromthe corresponding regions can be directed toward a specific locationoff-axis at an angle theta, thus essentially creating a positive focalpoint for the light output from the light emitting device. In anotherembodiment of this invention, the light output from one or more regionsfrom the light output surface regions diverge relative to each other,thus creating a type of negative (or virtual focus) for the lightemitting device.

Adjustable Light Output Profile

In one embodiment of this invention, at least one of the peak directionor the FWHM of the angular light output profile in one or more outputplanes of a light emitting device is manually or electronicallyadjustable by rotating around a first axis or translating in a firstdirection one or more of the lightguide, light redirecting element,light scattering lens, volumetric light scattering element, lightfiltering directional control element, prismatic collimating film,position or orientation of a light source such as an LED, ornon-symmetric prismatic light redirecting film such as Image DirectingFilm or Transmissive Right Angle Film, both produced by 3M. In anotherembodiment of this invention, the peak direction or the FWHM of theangular light output profile of a light emitting device is adjustableelectronically without any moving parts by using an electronicallyreconfigurable diffusing element such as a Polymer Dispersed LiquidCrystal (PDLC) element. A PDLC can be switched from a substantiallydiffuse state to a substantially clear state by the application of anelectric voltage in the regions corresponding to at least one of thelight reflecting regions, light absorbing regions, light transmittingregions, or region above the lenticular lens array of a light filteringdirectional control element. In one embodiment, the light emittingdevice can be electronically controlled to switch from a light outputprofile of less than 10 degrees FWHM to one that is greater than 40degrees within at least one light output plane.

FIG. 1 shows a prior art light guide section 10 in a backlight, wherewhite dots 12 scatter the light in a Lambertian-like manner, thussending a significant amount of light toward the light source 14 (i.e.,back scattering). A large percentage of this light is lost (i.e., itescapes the light guide and is therefore unusable) when it reaches theedge 16 of the light guide 10 where the light was coupled in originally.As shown in FIG. 1, light reflecting off of the white dots 12 isscattered in the ±y and ±x and +z directions. This is inadequate controlover the scattering, and light sent to wide angles is lost.

FIG. 2 illustrates one embodiment of an enhanced LCD backlight of thisinvention, wherein light from a CCFL 14 is directed into the edge 16 ofa volumetric scattering light guide 10 containing asymmetric particles18. In this configuration, more control over the scattering is obtainedby using a volumetric, asymmetric light guide. This volumetricscattering light guide 10 will have less backscatter and more light willbe coupled out of the volumetric scattering light guide 10 in theforward direction (+z direction). The asymmetric particles 18 willpreferentially scatter light in a forward direction (+x direction) andout of the volumetric scattering light guide 10 (+z direction). The maybe formed by casting or forming a sufficiently thick polymer material 20containing asymmetric particles 18. A further embodiment of an enhancedbacklight may include additional light diffusing films or regions andcollimating sheets. Birefringent films and reflective polarizers mayalso be used to increase backlight efficiency.

FIG. 3 illustrates a perspective view of the backlight volumetricscattering light guide 10 shown in FIG. 2. In this embodiment, theasymmetric particles 18 in the volumetric scattering light guide 10predominantly scatter light from the CCFL 14 that is traveling in the +xdirection into the ±z directions. The −z direction scattering will reacha reflector and be re-directed in the +z direction. When linear CCFLs 14are used, very little scattering is needed in the y direction, becausethe lamp 14 is essentially a linear extended source in the y direction.Thus, an asymmetric scattering region is more efficient, because itpredominantly scatters light in the ±z directions and very little, ifany, in the ±y directions.

FIG. 4 illustrates an embodiment of this invention of an enhanced LCDbacklight wherein LEDs 14 are used with an asymmetrically scatteringlight guide 10. If LEDs 14 are used to couple light in from the edge ofthe light guide 10, more control over the light can be achieved due tothe ability to substantially collimate light from the LEDs 14 usingcollimating lenses 24. The directionality of the light from LEDs can bemore tightly controlled, relative to the CCFLs. As a result, the angulardistribution of light can be better controlled by using an asymmetricscattering region. Thus, the light from the LEDs 14 is travelingsubstantially only in the +x direction with very little divergence inthe ±y directions. The asymmetric particles 18 are aligned such thatthey will diffuse the light predominantly out of the light guide 10.

FIG. 5 illustrates a further embodiment of this invention of an enhancedLCD backlight wherein the density of particles 18 varies throughout thelength of the light guide 10. In a backlight volumetric scattering lightguide 10 containing uniform particle densities throughout the volumetricscattering light guide 10 and a high concentration of particles 18, thelight intensity uniformity can be poor. With a uniform high density ofparticles 18, more light is scattered out of the volumetric scatteringlight guide 10 closer to the light source 14. In a printed dot lightguide, the non-uniformity is controlled by the size and spacing of thewhite dots with typically more printed white area further from the lightsource. By varying the density (concentration) of asymmetric particles18 in different regions of the light guide 10 a more uniform output canbe achieved. As shown in FIG. 5, less of the light from the LEDs 14reaches the particles 18 in the region 26 near the LEDs 14 as comparedto the region 28 further from the sources 14. With differentconfigurations of light sources 14 (more than one edge, more than onesource per edge, etc.) the optimum variation in particle density couldchange from low to high to low density regions. Other density patternsor variations are envisioned that can provide a uniform light outputintensity for a specific light source arrangement. The variation inparticle density may be controlled in the manufacturing process of theasymmetric light guide 10. For example, an extruder for a film can bedesigned to accept feeds from different mixtures containing differentconcentrations of particles within the same host matrix. This film orsheet could be extruded sufficiently thick to function as a light guidefor a specific light source or multiple sheets or film layers could becombined. The thickness is also reduced as shown in FIG. 5 because ofthe wedge shape of the light guide 10. In this manner, the wedge shapehelps reflect light from the surfaces or a reflector 22 such that it canescape the total internal reflection condition and be a more uniformbacklight.

LED based backlights can also use the side emitting LEDs 14 such asthose manufactured by LUMILEDS (FIG. 6). These side emitting LEDs 14 canbe used in the central portion of a light guide such that the LEDs 14are in a row and the light output totally internally reflects in thelight guide 10 from the center line outwards as shown in FIG. 7 (PriorArt). As shown in FIG. 7, the light from the LEDs 14 enters through thehole in the light guide 10 and is totally internally reflected withinthe light guide 10. If one were to use printed white dots or an HSOTlight guide, the light would scatter into undesirable angles and thesystem would be less efficient. The line configuration of the LEDs 14provides light along the ±y directions. A symmetric diffuser placed ontop of the light guide 10 of FIG. 4 or an HSOT would scatter lightunnecessarily in the ±y directions.

Asymmetric scattering regions allow additional control of the scatteredlight. The scattering regions may be located within the light guideregion, or alternatively, the asymmetric scattering regions may belocated above or below a substantially transparent light guide region.In configurations where the scattering regions are optically coupled tothe transparent light guide and the host matrix have similar refractiveindices, the scattering regions may become part of the light guide. Inother words, the light may scatter in the scattering regions and aportion of this light may be totally internally reflected at anair-scattering region interface.

FIG. 8 illustrates another embodiment of this invention wherein a lightscattering region 30 is optically coupled to a substantiallynon-scattering region of a light guide 10 with the scattering particles18 in the film 30 arranged parallel to a line of LEDs 14 located withinthe planar region of the light guide 10. By aligning the particles 18parallel to the line of LEDs 14 the light will more efficiently scatterout of the light guide 10 by scattering only in the ±z directions. Thelight from the LEDs 14 does not need to be substantially scattered inthe ±y directions. The reflector 22 beneath the light guide 14 willre-direct light in the −z direction to the +z direction out of the lightguide 10. More than one light scattering film 30 or region with the sameor different alignment axis may be used to achieve a desired angularprofile of light output.

FIG. 9 illustrates an embodiment of this invention wherein asubstantially planar asymmetric light scattering region 32 is located onthe underside of a light guide 10 with a reflector 22 beneath. Lightfrom two opposite ends of the light guide 10 enter the edge from twoCCFL lamps 14. A portion of the light that reaches the asymmetricdiffusive region 32 scatters in the ±z directions. There is very littlescatter in the ±y directions. The light that does not scatter reachesthe reflector 22 and either scatters on the way back through the region32 or is directed through total internal reflection to another region ofthe scattering film. As a result, less light is scattered back towardsthe edges or sides and more is directed out of the light guide 10 in the+z direction.

FIG. 10 illustrates a further embodiment of an enhanced backlightwherein the density of asymmetric particles 18 varies related to thedistance from the light sources 14. As shown in FIG. 10, the regions 26closer to the CCFLs 14 contain a lower density of asymmetric lightscattering particles 18 relative to the central portion 28. This createsa more uniform light output with the scattering effects. The light guide10 may also be tapered and the backlight can contain additionalsymmetric or asymmetric diffusers, reflective polarizers, or collimatingfilms between the light guide and the polarizer of the liquid crystalcell.

FIG. 11 shows another embodiment of this invention of a light emittingdevice comprising a light guide 10 with two asymmetric scatteringregions 32 and 34 aligned orthogonally between a reflective surface 22and a light guide 10. The light from the CCFL 14 aligned in the ydirection will reach the y-aligned asymmetric region 32 and most of thelight will scatter in the ±z directions and not be scatteredunnecessarily in the x direction. The light from the CCFL 14 aligned inthe x direction will substantially pass through the y-aligned asymmetricregion 32 and pass on to the x-aligned asymmetric region 34. This lightwill then be scattered predominantly in the ±z directions without havingbeen scattered unnecessarily in the y direction. The light that isscattered in the −z direction will be reflected from the reflector 22and re-directed out of the light guide in the +z direction. As shown inFIG. 11, the light scattering regions 32 and 34 are films locatedbeneath the light guide 10. The density, particle asymmetry andrefractive index difference, and thickness of the two orthogonalscattering regions 32 and 34 control the horizontal and vertical lightscattering profile (thus viewing zones). These parameters can beadjusted individually for either layer to control the light profile.Alternatively, the light scattering regions 32 and 34 could be locatedin separated (spaced apart) regions to create a multi-phase scatteringregion that will reduce the speckle contrast of the display. Asymmetricand symmetric particles 18 may be located within the same region of thelight guide 10. The axis of the asymmetric scattering regions 32 and 34may be aligned at an angle theta with respect to each other. As shown,two CCFLs 14 are used. One, or more than two CCFLs or LEDs 14 may alsobe used in this configuration.

FIG. 12 shows another embodiment of a light emitting device wherein twoasymmetrically scattering regions 32 and 34 aligned at an angle withrespect to each other are place between a light guide 10 and thepolarizer optically coupled to a liquid crystal cell. In the drawing,the scattering axes are perpendicular to each other. The polarizer,liquid crystal cell, and other optical films are not shown for clarity.The light from the each of the CCFLs 14 scatters similar to that in FIG.11.

An additional embodiment of a light emitting device is shown in FIG. 13.This configuration is similar to the one in FIG. 12 except that one ofasymmetric light scattering regions 34 is located beneath the lightguide 10 with the other region 32 located above the light guide 10. LEDs14 may be used instead of CCFLs 14 in this configuration. By spacingapart the scattering regions 32 and 34 with the light guide 10, thespeckle contrast can be reduced.

FIG. 14 shows another embodiment of this invention of an enhancedbacklight light guide wherein a light guide 10 that is tapered from bothends contains asymmetric particles 18 that are substantially aligned inthe y direction. The tapering causes more light to be coupled out of thelight guide 10 toward the center, giving a more uniform lightdistribution. The tapering of the light guide 10 could also be used withLEDs 14. The tapering could also be in the y direction as well astapered in the x and y directions.

FIG. 15 illustrates a further embodiment of this invention wherein thelight guide is composed of two asymmetric scattering regions 32 and 34.The light is scattered similar to the embodiment illustrated in FIG. 11except that the light is totally internally reflected within one or moreof the light scattering regions 32 and 34. This eliminates the need fora separate non-scattering light guide and the associated assemblyprocess. The light scattering regions 32 and 34 could be constructed ofsufficient thickness such that the light from the light sources 14(LEDs, CCFL, etc) could be coupled into the scattering regions 32 and34. As discussed in the embodiment of FIG. 11, by using two orthogonalscattering regions 32 and 34, the horizontal and vertical scattering(thus viewing zones) can be easily controlled. The parameters of thescattering region(s) 32 and 34 can be controlled to create asufficiently uniform brightness across the backlight. The orthogonallight scattering particles 18 may be combined within the same regionthat also functions as a light guide. In a further embodiment of thisinvention, the volumetric scattering lightguide is comprised of twosubstantially symmetric scattering regions in a first output plane.

FIG. 16 illustrates a further embodiment of this invention of anenhanced liquid crystal display wherein the light guide 10 of FIG. 9 iscombined with two polarizers 36 and liquid crystal cell 38 (whichcontains glass substrates, spacers, alignment regions, liquid crystalmaterial and other materials known to those in the industry, not shown).By careful design of the parameters of the light scattering region 32 inFIG. 16, collimating films may not be needed to achieve a liquid crystaldisplay with a desired viewing angle. For example, by using a lightscattering region 32 with asymmetrically shaped particles as in FIG. 16,the light from the LCD exits substantially diffused in the ±x directionsand much less in the ±y directions. This LCD would have a wide viewingangle in the horizontal direction and a small vertical viewing angle andthe resulting brightness would be much higher than that of a comparablebacklight with a wide horizontal and vertical viewing angle.

FIG. 17 illustrates a further embodiment of this invention of a lightemitting device wherein two substantially crossed collimating films 40and 42 such as Brightness Enhancement Film from 3M or RCF filmmanufactured by REFLEXITE are added to the configuration of FIG. 16.Collimating films 40 and 42 can direct at least a portion of the lightfrom wide angles to angles closer to the normal (+z direction). Thiscould be used to further increase the on-axis brightness of the LCDrelative to that of FIG. 16. The light scattering region 32 parameterscan be adjusted in conjunction with the collimating films 40 and 42 toachieve the desired angular light profile output and uniformity. Thecollimating films 40 and 42 may contain prismatic structures 44 withparameters that vary across the film. The height of the prismaticstructures 44 can vary lengthwise along the prisms 44. By varying theheight of the prisms 44, other films in contact with the sheet do notproduce undesirable optical effects such as Moiré. The pitch of theprisms 44 may be non-constant. The pitch could be randomly chosen or itcould be pre-determined to be a non-regular spacing. The apex angle ofthe prisms 44 could also vary with a regular or irregular pitch. Thepitch of the prisms 44 could also vary lengthwise along the prisms. Theprisms 44 could extend at an angle relative to the edge of the film. Byreducing the regularity of the prismatic structure 44, optical effectssuch as Moiré can be reduced. Combinations of these variations on theprismatic structure 44 can be envisioned and are incorporated herein.

FIG. 18 illustrates a further embodiment of this invention of a lightemitting device wherein a diffuser 46 is added to the light guideconfiguration of FIG. 17. A symmetric or asymmetric diffuser 46 is addedbetween the light guide 10 and the collimating films 40 and 42. Thediffuser 46 can reduce the appearance of speckle from the backlight.This is more critical when LEDs are used as light sources 14 versusCCFLs. The additional diffuser 46 will also reduce the appearance ofnon-uniformities in the backlight intensity variations. A diffusivesurface relief structure may be used beneath the collimating filmstructures 40 and 42 as is the case with the RCF film.

FIG. 19 illustrates a further embodiment of this invention of anenhanced LCD backlight wherein a reflective polarizer 48 is positionedabove the top collimating film 40 and the liquid crystal cell 38 andpolarizers 36. A reflective polarizer 48 is often used with LCDbacklights to recycle the light such that more can be used. Thereflective polarizer 48 is aligned to transmit light of the desiredpolarization (S-wave, for example) and reflect P-wave polarized light.By passing back through the diffusers after reflection and scatteringthe polarization of this light can be rotated such that upon reachingthe reflective polarizer 48 for a second time, more can pass through.The polarization can be rotated due to stress birefringence of one ormore of the optical films or light guides or the polarization can bede-polarized be the scattering off the white dots. In one embodiment ofthis invention, the asymmetric scattering regions 32 can be designed tohave a specific birefringence such that the light is rotated efficientlysuch that a higher percentage of the light can pass back through thereflective polarizer 48 on the second pass. Additionally, because thecontrol of the light scattering is more efficient with the volumetricasymmetric scattering regions 32, the recycled light also scatters moreefficiently, thus more of it passes through the reflective polarizer 48on the second or later passes and the display is brighter.

FIG. 20 illustrates a further embodiment of this invention of a lightemitting device wherein one of the asymmetric scattering regions islocated within the collimating film 42. By combining the asymmetricscattering region and the collimating film into one film 42, the displaythickness can be reduced and the assembly costs can be lowered. Theasymmetrically scattering collimating film 42 can contain asymmetricallyshaped light scattering particles 18 within the substrate 50, theprismatic structures 44, or in both regions. One or more of theseregions 50 and 44 may contain substantially symmetric particles 18. Thedetails of such asymmetric collimating films 42 are further described inU.S. Patent Application No. 60/605,956, the entire contents of which areincorporated herein by reference. The embodiments described for anenhanced light diffusing sheet can be used with a backlight, lightemitting device, optical composite, optical component, or lightguidedescribed herein.

FIG. 21 illustrates a further embodiment of this invention of a lightemitting device wherein the light guide 10 is made using a highrefractive index material. By optically coating a low refractive indexregion 52 on the top surface of the light guide 10, an additional filmsuch as a collimating film 42 may be optically coupled to the surface.This can reduce the number of air gaps required and simplify theassembly process. The high and low refractive index materials can stillenable a light guide that will allow the light to reflect multiple timesto create uniformity across the backlight. The low refractive indexmaterial could be an aerogel, sol-gel or plastic with microscopic pores.It may also be an adhesive such that it can also function to adhere afilm such as the collimating film 42 to the light guide 10. The highrefractive index material could be commonly known high refractive indexpolymers or other material such as Nitto Denko's high-refractive indexthermosetting polymer capable of reaching a refractive index of 1.76(Nitto Denko Press Release, 11 Nov. 2003). Additional diffusers,collimating films 40, and polarizers 36 may be used to produce thedesired light output. CCFLs or LEDs 14 may be used in conjunction withthe high refractive index light guide 10. In another embodiment of thisinvention, a low refractive index planarization layer is used above thecollimating film 42 so that an additional collimating film 40 may beoptically coupled to the first collimating film 42 and retain its lightcollimating characteristics. In a further embodiment, this secondcollimating film 40 could have a planarization layer, thus allowingother films such as a reflective polarizer to be optically coupled toit, further reducing system thickness and difficulties associated withrequired air gaps.

FIG. 22 illustrates an embodiment of this invention wherein a lightguide 10 containing a higher concentration of dispersed particles 18directly above fluorescent lamps 14 in a backlight can improve theluminance uniformity of the backlight. In the direct-lit backlightillustrated, the illuminance on the light scattering region 32 of thelight guide 10 directly above the lamps 14 is higher because it iscloser to the light sources 14 and occupies a larger angular extent ofthe radiance in that region 32. With a traditionally symmetric diffuseror light guide plate, the luminance from the light guide 10 would behigher in the regions near the light sources 14. With an asymmetricdiffusing region 32, the luminance uniformity across the light guide 10would still be improved, although it is unlikely to be sufficientlyuniform for a thin diffuser. The light scattering region 32 of FIG. 22contains regions with higher concentration of asymmetric particles 18 inthe regions closer to the light source. Thus, the regions with the highilluminance spread the light into larger angles (in the x-z plane). Inthe regions corresponding to locations further from a light source 14,the concentration is reduced, allowing the light to pass through thelight scattering region 32 and contribute to illuminance averaging bycombining with that of another light source. By scattering the light inthe higher illuminance regions into larger angles, the uniformity isimproved. The uniformity can be further increased by adding a secondlight diffusing region within the light guide 10 or between the lightguide 10 and the display. A second light diffusing region will reducethe speckle contrast of the display and increase the uniformity anddisplay contrast. In addition to a variation in dispersed phaseconcentration, a reduction in thickness in regions between the lightsources 14 can achieve a similar affect. In a further embodiment, boththe concentration and the thickness can be reduced as illustrated inFIG. 5.

FIG. 23 illustrates an embodiment of this invention wherein a lightguide 10 comprises a light scattering region 32 and a non-scatteringregion 54. The scattering region 32 contains non-spherical dispersedphase domains 18 and can be used to create the uniform luminancebacklight of FIG. 9.

FIG. 24 illustrates an embodiment of this invention wherein a lightguide 10 comprises a light scattering region 32 and a reflector 22 whichmay be diffusely reflecting and can be used to scatter the incidentlight into angles that do not satisfy the total internal reflectioncondition at the output boundary. The scattering region 32 containsnon-spherical dispersed phase domains 18.

FIG. 25 illustrates an embodiment of this invention wherein a lightguide 10 comprises a light scattering region 32 and a non-scatteringregion 54. The scattering region 32 contains non-spherical dispersedphase domains 18 with a spatially varying concentration and can be usedto create the uniform luminance backlight of FIG. 22.

FIG. 26 is a cross-sectional side view of a light emitting device 2600comprising a volumetric scattering lightguide 2602 with a low refractiveindex region 2604 optically coupled to a volumetric scattering region2606 and a first non-scattering region 2603. A light source 2601 isdisposed to couple light into the volumetric scattering lightguide 2602.The low refractive index region comprises a low refractive indexmaterial 2605. The volumetric scattering region comprises a matrixmaterial 2608 with dispersed phase domains 2607. A first portion oflight 2609 from the light source 2601 is directed into the volumetriclight scattering lightguide 2602, totally internally reflects throughthe first non-scattering region 2603, passes through the low refractiveindex region 2604, scatters within the volumetric light scatteringregion 2606, and escapes the volumetric light scattering lightguide2602. The first portion of light 2609 exits the volumetric scatteringlightguide 2602 through the volumetric light scattering region 2606 atthe first light emitting surface 2612 on the same side of the firstnon-scattering region 2603 as the volumetric light scattering region2606. A second portion of light 2611 from the light source 2601 scattersfrom the volumetric scattering region 2606 back through the firstnon-scattering region 2603 and exits the volumetric scatteringlightguide 2602 through the first non-scattering region at the secondlight emitting surface 2613 on the opposite side of the firstnon-scattering region 2603 as the volumetric light scattering region2606. A third portion of light 2610 from the light source 2601 travelsat an angle such that it totally internally reflects at the interfacebetween the first non-scattering region 2603 and the low refractiveindex region 2604. The first light flux 2614 exits the first lightemitting surface 2612 of the volumetric scattering lightguide 2602 onthe same side of the first non-scattering region 2603 as the volumetriclight scattering region 2606. The second light flux 2615 exits the lightemitting surface 2613 of the volumetric scattering lightguide 2602 onthe opposite side of the first non-scattering region 2603 as thevolumetric light scattering region 2606. The low refractive index region2604 enables a stronger volumetric light scattering region (such as adiffuser with a larger full angular width at half maximum intensity)without creating a non-uniform spatial luminance on the first lightemitting surface 2612 or the second light emitting surface 2613 inregions closer to the light source 2601. The low refractive index regionallows light 2610 through a first high angular range to TIR at theinterface between the first non-scattering region 2603 and the lowrefractive index region 2604. Thus, the low refracting index region canfunction as a high angle limiter by preventing (by TIR) light from afirst high angle range to reach the volumetric light scattering regionwhere it could be scattered such that it escapes the volumetric lightscattering region.

FIG. 27 is a cross-sectional side view of the light emitting 2600 deviceof FIG. 26 illustrating several component dimensions. The distance, D,is the distance between the edge of the first non-scattering region 2603where light from the first light source 2061 is coupled into thevolumetric scattering lightguide 2062 to the edge of the volumetriclight scattering region 2606. The length, L, is the length of thevolumetric light scattering lightguide 2602 in a direction parallel tothe light source optical axis 2701 of the first light source 2601. Thethickness, t, is the thickness of the first non-scattering region 2603.

FIG. 28 is a cross-sectional side view of a light emitting device 2800comprising a volumetric scattering lightguide 2602 with a spatiallyvarying low refractive index region 2801. A fourth portion of light 2802from the light source 2601 is coupled into the volumetric scatteringlightguide 2602, totally internally reflects within the non-scatteringregion 2603, passes through the low refractive index material 2605,scatters within the matrix material 2608 comprising dispersed phasedomains 2607, and escapes the volumetric scattering lightguide 2602. Afifth portion of light 2803 from the light source 2601 coupled into thevolumetric scattering lightguide 2602 totally internally reflects andpasses through the first non-scattering region 2603, passes through thevolumetric light scattering region, and scatters in the matrix material2608 comprising dispersed phase domains 2607.

FIG. 29 is a top view of the light emitting device 2800 of FIG. 28comprising a volumetric scattering lightguide 2602 with a spatiallyvarying low refractive index region 2801. FIG. 29 illustrates a firstspatial region 2901 where the low refractive index region 2605 isdisposed between portions of the matrix material 2608 and the firstnon-scattering region 2603. The matrix material 2608 of the volumetriclight scattering region is directly optically coupled to the firstnon-scattering region 2603 of the volumetric scattering lightguide 2602in a second spatial region 2902. The light sources 2601 are arranged inlinear arrays 2903 along four edges of the first non-scattering region2603 of the volumetric scattering lightguide 2602.

FIG. 30 is a cross-sectional side view of a light emitting device 3000comprising a diffusely reflecting optical element 3002 on the same sideof the volumetric scattering lightguide 2602 as the volumetricscattering region 2606. The diffusely reflecting optical element 3002 isseparated from the volumetric scattering lightguide 2602 (or lightscattering region 2606) by an air gap region 3001 wherein the diffuselyreflecting optical element 3002 is not optically coupled to thevolumetric scattering lightguide 2602. A sixth portion of light 3003from the light source 2601 coupled into the volumetric scatteringlightguide 2602 totally internally reflects, passes through the firstnon-scattering region 2603, passes through the low refractive indexregion 2604, passes through the matrix material 2608 comprisingdispersed phase domains 2607 and escapes the volumetric scatteringlightguide 2602. This sixth portion of light 3003 then diffuselyreflects from the diffusely reflecting optical element 3002, passes backthrough the matrix material 2608 comprising dispersed phase domains2607, passes through the low refractive index region 2604, passesthrough the first non-scattering region 2603 and escapes the volumetricscattering lightguide 2602 through the second light emitting surface2613.

A seventh portion of light 3004 from the light source 2601 is coupledinto the volumetric scattering lightguide 2602, totally internallyreflects in the first non-scattering region 2603, passes through the lowrefractive index region 2604 and the volumetric scattering region 2606,totally internally reflects at the interface between the matrix material2608 and the air gap 3001 back toward the low refractive index region2604, passes through the low refractive index region 2604 and the firstnon-scattering region 2603, and escapes the volumetric scatteringlightguide 2602 through the second light emitting surface 2613.

By employing an air gap 3001 between the volumetric light scatteringlightguide 2602 (or volumetric light scattering region 2606, or matrixmaterial 2608) and the diffusely reflecting optical element 3002, theseventh portion of light 3004 is totally internally reflected at theinterface between the matrix material 2608 and the air gap 3001 beforereaching the diffusely reflecting optical element 3002. If the diffuselyreflecting optical element 3002 were optically coupled to the volumetricscattering lightguide 2602 (or light scattering region 2606, or matrixmaterial 2608), a significant amount of incident light would bescattered by the diffusely reflecting optical element 3002 into anglescloser to the normal to the outer surfaces of the volumetric scatteringlightguide 2602 such that a bright region corresponding to thesignificant amount of light extracted from the lightguide in that regioncould reduce the spatial luminance uniformity measured in the x-y planeat the second light emitting surface 2613.

FIG. 31 is a cross-sectional side view of a light emitting device 3100comprising a diffusely reflecting optical element 3002 on the oppositeside of the volumetric scattering lightguide 2602 as the volumetricscattering region 2606. The diffusely reflecting optical element 3002 isseparated from the first non-scattering region 2603 of the volumetricscattering lightguide 2602 by an air gap region 3001 wherein thediffusely reflecting optical element 3002 to is not optically coupled tothe volumetric scattering lightguide 2602. A first portion of light 2609from the light source 2601 is coupled into the volumetric scatteringlightguide 2602, totally internally reflects, passes through the firstnon-scattering region 2603, passes through the low refractive indexregion 2604, scatters within the matrix 2608 material due to thedispersed phase domains 2607 and escapes the volumetric scatteringlightguide 2602 through the first light emitting surface 2612. An eighthportion of light 3101 from the light source 2601 coupled into thevolumetric scattering lightguide 2602 totally internally reflects in thefirst non-scattering region 2603, passes through the low refractiveindex region 2604, scatters from dispersed phase domains 2607 within thematrix material 2608 toward the low refractive index region, passesthrough the low refractive index region 2604 and the firstnon-scattering region 2603, and escapes the volumetric scatteringlightguide 2602. This eighth portion of light 3101 then diffuselyreflects from the diffusely reflecting optical element 3002, passes backthrough the first non-scattering region 2603, the low refractive indexregion 2604, and the matrix material 2608 where it then escapes thevolumetric scattering lightguide 2602 through the first light emittingsurface 2612.

By employing an air gap 3001 between the first non-scattering region2603 and the diffusely reflecting optical element 3002, the firstportion of light 2609 and the eighth portion of light 3101 are totallyinternally reflected at the interface between the first non-scatteringregion 2603 and the air gap 3001 before reaching the low refractiveindex region 2604. If the diffusely reflecting optical element 3002 wereoptically coupled to the volumetric scattering lightguide 2602 (or thefirst non-scattering region 2603), a significant amount of light wouldbe scattered by the diffusely reflecting optical element 3002 intoangles closer to the normal to the first light emitting surface 2612 ofthe volumetric scattering lightguide 2602 such that a bright regioncorresponding to the significant amount of light extracted from thelightguide in that region would reduce the spatial luminance uniformitymeasured in the x-y plane at the first light emitting surface 2612.

FIG. 32 is a cross-sectional side view of a light emitting device 3200comprising a curved volumetric scattering lightguide 3201. A ninthportion of light 3203 from the light source 2601 is coupled into thecurved volumetric scattering lightguide 3201, totally internallyreflects, passes through the first non-scattering region 2603, passesthrough the low refractive index material 2605, scatters within thematrix material 2608 due to the dispersed phase domains 2607 and escapesthe curved volumetric scattering lightguide 3201 through the first lightemitting surface 2612. A tenth portion of light 3202 from the lightsource 2601 is coupled into the curved volumetric scattering lightguide3201, totally internally reflects, passes through the firstnon-scattering region 2603, passes through the low refractive indexmaterial 2605, backwardly scatters within the matrix material 2608 dueto the dispersed phase domains 2607 and escapes the curved volumetricscattering lightguide 3201 through the second light emitting surface2613. The curved volumetric scattering lightguide can be employed tocontrol the angular output of the light from the light emitting deviceand also be used to reduce glare seen on the second light emittingsurface 2613 by reducing the visibility of the surface when the surfaceis viewed from an angle significantly off of the nadir due to theblocking of the view by the curved shape. For example, the entirety ofthe right side of the emitting surface 2613 will not be visible (thusglare will be reduced) when viewing the light emitting device 3200 atangles such as 45 degrees from the nadir on the right side due to thevisibility being block by the light source, input edge, and possiblyother components on the right side of the lightguide. The first lightflux 2614 exits the light emitting surface 2612 of the curved volumetricscattering lightguide 3201 on the same side of the first non-scatteringregion 2603 as the volumetric light scattering region 2606. The secondlight flux 2615 exits the light emitting surface 2613 of the curvedvolumetric scattering lightguide 3201 on the opposite side of the firstnon-scattering region 2603 as the volumetric light scattering region2606. In one embodiment of this invention, the angular output FWHM ofthe light exiting the light emitting device from a first light emittingsurface or a second light emitting surface is reduced due to thecurvature of the light emitting device.

FIG. 33 is a cross-sectional side view of a light emitting device 3300comprising a volumetric scattering lightguide with a low refractiveindex region 2604 and a specularly reflecting optical element 3301optically coupled to the volumetric light scattering region 2606. Aneleventh portion of light 3302 from the light source 2601 coupled intothe volumetric scattering lightguide 2602 totally internally reflects,passes through the first non-scattering region 2603, passes through thelow refractive index region 2604, passes through the matrix material2608 comprising dispersed phase domains 2607, specularly reflects fromthe specularly reflecting optical element 3301, passes back through thematrix material 2608, passes through the low refractive index region2604, passes through the first non-scattering region 2603 and escapesthe volumetric scattering lightguide 2602 through the second lightemitting surface 2613. The specularly light reflecting optical elementdoes not substantially increase or decrease the angle from the normal atthe surface similar to a total internal reflection at an interfacebetween the volumetric light scattering region and an air gap, thus itdoes not directly increase the light output coupling or amount of lightthat exits the volumetric scattering lightguide. However, the specularlyreflecting optical element reflects a portion of light from narrowangles to the surface normal of the light emitting surface that wouldotherwise escape the volumetric scattering lightguide. Thus, for examplewith a specularly reflecting film which specularly reflects 80% of theincident light, 80% of the light which would otherwise exit thelightguide from the surface would be reflected back into the lightguideto eventually exit the lightguide from the opposite surface or beabsorbed.

FIG. 34 is a perspective view of a light emitting device 3400 comprisinga volumetric scattering lightguide 2602 with a low refractive indexmaterial 2605 and asymmetric dispersed phased domains 3401 within amatrix material 2608. A twelfth portion of light 3402 from the lightsource 2601 is coupled into the volumetric scattering lightguide 2602,totally internally reflects, passes through the first non-scatteringregion 2603, passes through the low refractive index material 2605,anisotropically scatters within the matrix 2608 material due to theasymmetrically shaped dispersed phase domains 3401 and escapes thevolumetric scattering lightguide 2602 through the first light emittingsurface 2612.

FIG. 35 is a perspective view of a light emitting device 3500 comprisinga matrix material 2608 with dispersed phase domains 2607 which aresubstantially spheroidal between a low refractive index material 2605and a second non-scattering region 3501. A thirteenth portion of light3502 from the light source 2601 is coupled into the volumetricscattering lightguide 2602, totally internally reflects, passes throughthe first non-scattering region 2603, passes through the low refractiveindex material 2605, passes through the matrix material 2608, passesthrough the second non-scattering region 3501 and escapes the volumetricscattering lightguide 2602 through the first light emitting surface2612. In one embodiment of this invention, the second non-scatteringregion serves at least one function selected from the group ofprotecting the volumetric scattering region, providing a material layerwith surface relief light extracting regions, providing a support layerfor a light redirecting element or additional scattering region,provides a base material for light extracting surface relief features,provides a carrier or support base material for the volumetric lightscattering region useful for the production and/or the physical couplingof the volumetric scattering region to the first non-scattering region.

FIG. 36 is a cross-sectional side view of a light emitting device 3600comprising a volumetric scattering lightguide 2602 with a low refractiveindex region 2604 and surface relief light extracting features 3601 onthe first non-scattering region 2603 of the volumetric scatteringlightguide 2602. A fourteenth portion of light 3602 from the lightsource 2601 is coupled into the volumetric scattering lightguide 2602,totally internally reflects, passes through the first non-scatteringregion 2603, passes through a surface relief light extracting feature3601 which enables it to escape the volumetric scattering lightguide2602. This fourteenth portion of light 3602 then passes through the airgap 3005, diffusely reflects from the diffusely reflecting opticalelement 3001, passes back through the air gap 3005, the firstnon-scattering region 2603, the low refractive index region 2604, thevolumetric scattering region 2606, and escapes the volumetric scatteringlightguide 2602 through the first light emitting surface 2612.

FIG. 37 is a cross-sectional side view of a light emitting device 3700comprising a volumetric scattering lightguide 2602 with a low refractiveindex material 2605 varying spatially in the x-y plane between thematrix material 2608 and the first non-scattering region 2603. Thematrix material 2608 of the volumetric light scattering region isoptically coupled to the first non-scattering region 2603 of thevolumetric scattering lightguide 2602 in a second spatial region 2902.The low refractive index material 2605 is disposed between and opticallycoupled to the matrix material 2608 of the volumetric light scatteringregion and the first non-scattering region 2603 of the volumetricscattering lightguide 2602 in a first spatial region 2901. A fourthportion of light 2802 from the light source 2601 is coupled into thevolumetric scattering lightguide 2602, pass into the non-scatteringregion 2603, passes into the matrix material 2608 and scatters backwardsfrom the dispersed phase domains 2607 into the non-scattering region,totally internally reflects in the first non-scattering region 2603 ofthe volumetric scattering lightguide 2602, passes through the lowrefractive index material 2605, scatters in the matrix material 2608comprising dispersed phase domains 2607, and escapes the volumetricscattering lightguide 2602 through the first light emitting surface2612. A fifth portion of light 2803 from the light source 2601 coupledinto the volumetric scattering lightguide 2602 totally internallyreflects in the first non-scattering region 2603 of the volumetricscattering lightguide 2602 at the first spatial regions 2901, passesthrough the first non-scattering region 2603, scatters in the matrixmaterial 2608 comprising dispersed phase domains 2607 and escapes thevolumetric scattering lightguide 2602 through the first light emittingsurface 2612.

FIG. 38 is a top view of the light emitting device 3700 of FIG. 37illustrating the second spatial regions 2902 in the x-y plane where thematrix material 2608 is directly coupled optically to the firstnon-scattering region 2603. The size, shape, or location of at least oneof the first spatial regions 2901 and second spatial regions 2902 mayvary in any direction in the x-y plane. As shown in FIG. 38, the secondspatial regions 2902 become closer together and slightly larger movingfrom the edge toward the center of the first non-scattering region 2603.In one embodiment of this invention, the spatial density of the firstspatial regions or second spatial regions increases from the edge towardthe center of the non-scattering region. In another embodiment of thisinvention, the size first spatial regions or second spatial regionsincreases from the edge toward the center of the non-scattering region.

FIG. 39 is a cross-sectional side view of a light emitting device 3900comprising a volumetric scattering lightguide 2602 with a low refractiveindex material 2605 and air gaps 3902 varying spatially in the x-y planebetween the matrix material 2608 and the first non-scattering region2603. The matrix material 2608 of the volumetric light scattering regionis directly optically coupled to the first non-scattering region 2603 ofthe volumetric scattering lightguide 2602 in second spatial regions2902. Air gaps 3902 are disposed between the matrix material 2608 andthe first non-scattering region 2603 in air gap regions 3901 in the x-yplane. A fourth portion of light 2802 from the light source 2601 iscoupled into the volumetric scattering lightguide 2602, totallyinternally reflects in the first non-scattering region 2603 of thevolumetric scattering lightguide 2602 at the air gap regions 3901,passes through the first non-scattering region 2603, through the lowrefractive index material 2605, scatters in the matrix material 2608comprising dispersed phase domains 2607, and escapes the volumetricscattering lightguide 2602 through the first light emitting surface2612. A fifth portion of light 2803 from the light source 2601 coupledinto the volumetric scattering lightguide 2602 totally internallyreflects at the second spatial region 2902 and the air gap region 3901within in the first non-scattering region 2603 of the volumetricscattering lightguide 2602, passes through the first non-scatteringregion 2603, and scatters in the matrix material 2608 comprisingdispersed phase domains 2607 and escapes the volumetric scatteringlightguide 2602 through the first light emitting surface 2612.

FIG. 40 is a top view of the light emitting device 3900 of FIG. 39illustrating the second spatial regions 2902 where the matrix material2608 is directly coupled optically to the first non-scattering region2603, and the air gap regions 3901 where there is an air gap between thematrix material 2608 and the first non-scattering region 2603, bothregions varying spatially in the x-y plane. The size, shape, or locationof one or more of the first spatial regions 2901, second spatial regions2902, and air gap regions 3901 may vary in any direction in the x-yplane. As shown in FIG. 40, the second spatial regions 2902 becomecloser together and slightly larger moving from the edge toward thecenter of the first non-scattering region 2603. In a direction withinthe x-y plane, the regions may vary in an alternating pattern such aslow refractive index region, air gap region, matrix material region, lowrefractive index region, air gap region, matrix material region, etc.,or they may vary in a quasi-random or random order or spatialarrangement. A first region may alternate more than one time with asecond region before a third region in a direction within the x-y plane.In one embodiment of this invention, the spatial density of at least oneof the first spatial regions, second spatial regions, and air gapregions increases or decreases in a direction within the x-y plane. Inone embodiment of this invention, the area or area fraction of at leastone of the first spatial regions, second spatial regions, or air gapregions increases or decreases in a direction within the x-y plane.

The different spatially varying regions may each contribute differentlyto a varying luminance or luminous output intensity pattern of lightexiting the volumetric scattering lightguide. In one embodiment of thisinvention, the first light output surface has a low level of luminanceor luminous output intensity directly above the air gap regions due tolight not being coupled into the volumetric scattering region, thus itis not scattered out of the volumetric scattering lightguide within thatregion. In another embodiment of this invention, the first light outputsurface has a high level of luminance or luminous output intensitydirectly above the second spatial regions due to more light beingcoupled directly into the matrix region (and ultimately scattered out ofthe lightguide) relative to the low refractive index regions. In afurther embodiment of this invention, the first light output surface hasa level of luminance or luminous output intensity directly above the lowrefractive index region in-between the levels of luminance or luminousoutput intensity above the air gap regions and the second spatialregions due a smaller amount of light being coupled into the matrixregion (and ultimately scattered out of the lightguide) relative to thesecond spatial regions because of the high angular cut-off at theinterface between the low refractive index material and the firstnon-scattering region.

FIG. 41 is a cross-sectional side view of a light emitting device 4100comprising a volumetric scattering lightguide 2602 wherein lighttraveling within the first non-scattering region 2603 at an angle largerthan the critical angle, Λ_(c), for the interface between thenon-scattering region 2603 and the low refractive index material 2605totally internally reflects. First light source light 4101 from a firstrange of angles from the light source 2601 is substantially symmetricabout the light source optical axis 2701 and is coupled into a second,smaller range of angles in the first non-scattering region 2603 of thevolumetric scattering lightguide 2602. From this first light sourcelight 4101, a fifteenth portion of light 4104 is incident on theinterface between the first non-scattering region 2603 and the lowrefractive index material 2605 at an angle from the surface normal 4103at the interface less than the critical angle, θ_(c), and is transmittedthrough the low refractive index region 2605, passes into the volumetriclight scattering region 2606 and is scattered and escapes the volumetriclight scattering lightguide 2602 through the first light emittingsurface 2612. Additionally, from the first light source light 4101, asixteenth portion of light 4105 is incident on the interface between thefirst non-scattering region 2603 and the low refractive index material2605 at an angle from the surface normal 4103 at the interface greaterthan the critical angle, θ_(c), and is reflected from the interface,back toward the second light emitting surface 2613 of the volumetricscattering lightguide.

The first light flux 2614 exits the first light emitting surface 2612 ofthe volumetric scattering lightguide 2602 on the same side of the firstnon-scattering region 2603 as the volumetric light scattering region2606. The light emitting device 4100 has a first light emitting deviceoptical axis 4106 for light flux 2614 leaving the first output surface2612 of the volumetric scattering lightguide 2602. In one embodiment ofthis invention, the first light emitting device optical axis is within 5degrees of angle from the normal to the first output surface of thevolumetric scattering lightguide selected from the group of 0 degrees,10 degrees, 20 degrees, 30 degrees, 40 degrees, 50 degrees, 60 degrees,70 degrees, 80 degrees, and 90 degrees.

The second light flux 2615 exits the second light emitting surface 2613of the volumetric scattering lightguide 2602 on the opposite side of thefirst non-scattering region 2603 as the volumetric light scatteringregion 2606. The light emitting device 4100 has a second light emittingdevice optical axis 4107 for light flux 2615 leaving the second outputsurface 2613 of the volumetric scattering lightguide 2602. In oneembodiment of this invention, the second light emitting device opticalaxis is within 5 degrees of an angle from the normal to the secondoutput surface of the volumetric scattering lightguide selected from thegroup of 0 degrees, 10 degrees, 20 degrees, 30 degrees, 40 degrees, 50degrees, 60 degrees, 70 degrees, 80 degrees, and 90 degrees.

FIG. 42 is a cross-sectional side view of a light emitting device 4200comprising a curved, tapered volumetric scattering lightguide 4206 and alight redirecting element 4204 with surface relief features 4205. Aseventeenth portion of light 4207 from the light source 2601 enters thecurved, tapered volumetric scattering lightguide 4206, travels throughthe curved, tapered non-scattering region 4201, scatters from thevolumetric scattering region 2606 back through the curved, taperednon-scattering region 4201, and exits the curved, tapered volumetricscattering lightguide 4206 through the curved, tapered non-scatteringregion 4201 at the light emitting surface 2613 on the opposite side ofthe curved, tapered non-scattering region 4201 as the volumetric lightscattering region 2606.

A eighteenth portion of light 4202 from the light source 2601 enters thecurved, tapered volumetric scattering lightguide 4206, travels throughthe curved, tapered non-scattering region 4201, through the lowrefractive index region 2604, scatters from the volumetric scatteringregion 2606 toward the light redirecting element 4204, is redirected bythe light redirecting optical element to an angle closer to the firstlight emitting device optical axis 4106.

A nineteenth portion of light 4203 from the light source 2601 enters thecurved, tapered volumetric scattering lightguide 4206, travels throughthe curved, tapered non-scattering region 4201 where the tapered,arcuate surface of the non-scattering region reflects the light at anangle closer to the normal of the opposite surface of the non-scatteringregion such that it travels into the low refractive index region 2604.This light then scatters from the volumetric scattering region 2606toward the light redirecting element 4204, is redirected by the lightredirecting optical element to an angle closer to the first lightemitting device optical axis 4106.

Additional diffusive layers or regions may be added to the top of thelight guide or bottom of the light guide. The volumetric scatteringregions described herein may be located at the top or bottom of thelight guide and may be aligned at an angle with respect to an edge. Thereflective films may be reflective polarizers. Light from LEDs may bedirected into one or more of the edges or surfaces of a light guide.Forward directing LEDs may be used behind an LCD panel wherein theasymmetric diffuse layers or regions will smooth out the intensity“hot-spots” where needed. For example, if three lines of forwarddirecting LEDs are located behind an LCD, an asymmetric diffuser whichwill diffuse the light more in a direction perpendicular to thedirection of the lines will more efficiently create a uniform intensitydistribution and result in higher forward light output.

The different variations in features and designs of the lightguides,optical elements and light emitting devices described herein can beenvisioned and include one or more combinations of the such elements tocreate a composite element.

Advantageous embodiments of the present invention are illustrated in thefollowing Examples. The following examples are given for the purpose ofillustrating the invention, but not for limiting the scope or spirit ofthe invention.

EXAMPLE 1

A light emitting device, in accordance with the present invention, canbe produced as described in FIG. 3, that is designed to have increasedoptical efficiency and therefore increased brightness relative toexisting backlights. This is possible because the volumetric asymmetricdiffusive region within the light guide allows for better control overthe light scattering. Light from two CCFL lamps is coupled into thelight guide. The light guide contains light scattering particles in ahost matrix material. The particle chosen may be a polystyrene bead ofdiameter 5 μm dispersed at concentrations up to 10% by volume in a hostmatrix of acrylic. Other choices of particles and host matrix mayprovide equivalent performance. Asymmetry and alignment of the asymmetrycan be created by stretching or extrusion processes. The asymmetricallydiffusing light guide can be created by extruding, casting or coating,the mixture containing the particles. The light guide may be 2.5 mm inthickness and this may be achieved by optically coupling more than onelayer or region containing asymmetric particles. One or more collimatingfilms such as 3M's Brightness Enhancement Film can be added to the topof the light guide to direct more light toward the on-axis direction. Areflective polarizer such as 3M's DBEF film can be added to increase thebrightness through polarized light recycling. To further reduce speckle,scattering regions can be separated by a non-scattering region.

EXAMPLE 2

A light emitting device, in accordance with the present invention, canbe produced as described in FIG. 11, that is designed to have increasedoptical efficiency and therefore increased brightness relative toexisting light emitting devices. This is possible because the volumetricasymmetric diffusive region below the light guide allows for bettercontrol over the light scattering. Two crossed asymmetric lightscattering regions are optically coupled to the non-scattering lightguide. Light from two CCFL lamps is coupled into the light guide. Theasymmetric light scattering regions contain asymmetric particles in ahost matrix material. The regions may be created by creating a mixtureconsisting of polystyrene bead particles of diameter 5 μm dispersed atconcentrations up to 10% by volume in a host matrix of acrylic. Otherchoices of particles and host matrix may provide equivalent performance.The asymmetrically diffusing regions can be created by extruding,casting or coating, the mixture containing the particles. These regionsor films may be optically coupled to the light guide film in a crossedconfiguration. Light scattering regions with different scatteringproperties may be used to give an asymmetric angle of view when coupledto an LCD. One or more collimating films such as 3M's BrightnessEnhancement Film can be added to the top of the light guide to directmore light toward the on-axis direction. A reflective polarizer such as3M's DBEF film can be added to increase the brightness through polarizedlight recycling. To further reduce speckle, the scattering regions canbe separated by a non-scattering region.

EXAMPLE 3

A light emitting device, in accordance with the present invention, canbe produced as described in FIG. 8, that is designed to have increasedoptical efficiency and therefore increased brightness relative toexisting backlights. This is possible because the volumetric asymmetricdiffusive region within the light guide allows for better control overthe light scattering. Light from more than one side-emitting RGB LEDscoupled into the light guide through holes in the light guide. The lightguide contains asymmetric light scattering particles aligned parallel tothe line of LEDs. The asymmetric light scattering light guide containasymmetric particles in a host matrix material. The regions may becreated by creating a mixture consisting of polystyrene bead particlesof diameter 5 μm dispersed at concentrations up to 10% by volume in ahost matrix of acrylic. Other choices of particles and host matrix mayprovide equivalent performance. The asymmetrically diffusing light guidecan be created by extruding, casting or coating, the mixture containingthe particles. The concentration of the light scattering particles canbe chosen to provide the optimum uniformity of light output from thelight guide. A reflector is optically coupled to the underside of thelight guide as illustrated in FIG. 8. One or more collimating films suchas 3M's Brightness Enhancement Film can be added to the top of the lightguide to direct more light toward the on-axis direction. A reflectivepolarizer such as 3M's DBEF film can be added to increase the brightnessthrough polarized light recycling. To further reduce speckle, thescattering regions can be separated by a non-scattering region.

EXAMPLE 4

A symmetric volumetric light scattering film with a angular FWHMintensity of the diffusion profile of 40 degrees by 40 degrees isproduced by extruding a film comprised of linear low densitypolyethylene domains dispersed within a polycarbonate matrix. A lowrefractive index material such as 3M Novec Electronic coating EGC-1730(a fluorosilane polymer carried in a hydrofluoroether solvent) is spraycoated on the surface of the film and the film inserted into the cavityof a mold with a quadric surface and held in place by a vacuum with thecoated surface facing the inner part of the mold. Light transmittingPMMA is injected into the mold such that it is optically coupled to thea surface of the volumetric light scattering film. The mold is cooledand the resulting tapered, volumetric scattering lightguide with aquadric surface and a polished edge is removed. A light source comprisedof an array of light emitting diodes (white Rebel LEDs produced byLumileds) on a circular metal core annulus is disposed next to the inputedge of the lightguide.

EXAMPLE 5

An anisotropic light scattering diffuser film produced as described inU.S. Pat. No. 5,932,342 is inserted into the cavity of a mold and heldin place by a vacuum. A light source comprised of an array of lightemitting diodes (white Rebel LEDs produced by Lumileds) on a metal corestrip. The diffuser is oriented with the domains substantially parallelto the optical axis of the LEDs. Light transmitting PMMA is injectedinto the mold such that it is optically coupled to the output surface ofthe LEDs and the anisotropic light scattering diffuser film. The mold iscooled and the resulting article is removed.

EXAMPLE 6

Two anisotropic light scattering diffuser films produced as described inU.S. Pat. No. 5,932,342 are inserted onto opposite surfaces of thecavity of a mold and held in place by a vacuum. A light source comprisedof an array of light emitting diodes (white Rebel LEDs produced byLumileds) on a metal core strip. The diffusers are oriented with thedomains substantially parallel to the optical axis of the LEDs. Lighttransmitting PMMA is injected into the mold such that it is opticallycoupled to the output surface of the LEDs and the anisotropic lightscattering diffuser films. The mold is cooled and the resulting articleis removed.

EXAMPLE 7

A 150 micron thick volumetric scattering film with substantiallysymmetric diffusion angles of 20 degrees by 20 degrees is formed byextruding a film from a blend of 80% PMMA and 20% COC by weight from atwin-screw extruder and film die. One surface of the film is spraycoated with Novec™ Electronic Coating EGC-1720 manufactured by 3M with arefractive index of 1.34. Using a Norland UV cured optical adhesive, thePC/COC volumetric light scattering film is optically coupled and adheredto a transparent sheet of 5 mm thick clear acrylic with a refractiveindex of 1.49 and a haze less than 20% to form a volumetric scatteringlightguide with a low refractive index region disposed between avolumetric scattering region and a non-scattering region.

EXAMPLE 8

A 150 micron thick volumetric scattering film with substantiallysymmetric diffusion angles of 20 degrees by 20 degrees is formed byextruding a film from a blend of 80% PMMA and 20% COC by weight from atwin-screw extruder and film die. A transparent, non-scatteringbi-axially oriented PET film is coated on one side with Novec™Electronic Coating EGC-1720 manufactured by 3M with a refractive indexof 1.34. Using a Norland UV cured optical adhesive, the PET film isoptically coupled and adhered to a transparent sheet of 5 mm thick clearacrylic with a refractive index of 1.49 and a haze less than 20% withthe PET in-between the adhesive and the EGC-1720 coating. Using aNorland UV cured optical adhesive, the PC/COC volumetric lightscattering film is optically coupled and adhered to the outer surface ofthe PET film to form a volumetric scattering lightguide with a lowrefractive index region disposed between a volumetric scattering regionand a non-scattering region.

EXAMPLE 9

A 150 micron thick volumetric scattering film with substantiallysymmetric diffusion angles of 20 degrees by 20 degrees is formed byextruding a film from a blend of 80% PMMA and 20% COC by weight from atwin-screw extruder and film die. Using a low refractive index UVcurable adhesive (Addison Clear Wave AC R262-MOD-5 with a refractiveindex of 1.455), the PC/COC diffusion film is optically coupled andbonded to a transparent sheet of 5 mm thick clear acrylic with arefractive index of 1.49 and a haze less than 10% to form a volumetricscattering lightguide with a low refractive index region disposedbetween a volumetric scattering region and a non-scattering region.

EXAMPLE 10

A transparent sheet of 5 mm thick clear acrylic with a refractive indexof 1.49 and a clarity greater than 80% is masked around the edges and ona first large face near the edges of the sheet. The surface is spraycoated with Novec™ Electronic Coating EGC-1720 manufactured by 3M with arefractive index of 1.34. A 150 micron thick volumetric scattering filmwith substantially symmetric diffusion angles of 20 degrees by 20degrees is formed by extruding a blend of 80% PMMA and 20% COC by weightthrough a twin-screw extruder and film die. Using a Norland UV curedoptical adhesive, the PC/COC volumetric light scattering film isoptically coupled and adhered to the coating on the sheet of acrylic toform a volumetric scattering lightguide with a low refractive indexregion disposed between a volumetric scattering region and anon-scattering region. Two linear arrays of LED's are disposed to couplelight into the volumetric scattering lightguide at opposite edges of thelightguide. A white PET voided diffusely reflecting film is positionednear the opposite surface of the non-scattering region as the volumetricscattering film with an air gap between the reflecting film and thevolumetric scattering lightguide. Light from the LEDs enters thevolumetric scattering lightguide and is coupled out due to thevolumetric scattering region in a uniform luminance pattern due to thelow refractive index coating reflecting high angled light from the LED'sthat would otherwise couple out of the lightguide from the volumetricscattering region and create a bright region and create a region with anon-uniform luminance. The resulting light emitting device has aluminance macro-uniformity and luminance micro-uniformity greater than70%.

EXAMPLE 11

A multi-layer thin volumetric scattering lightguide is formed byco-extruding three layers comprising of a layer of transparent acrylicmaterial (non-scattering region), a layer of FEP fluoropolymer (lowrefractive index region) further comprising a compatibilizer to enableadhesion to PMMA, and a third layer (volumetric scattering region) ofrubber-modified acrylic comprising 10% by weight of dispersed phasedomains of polyethylene. The multi-layer stack is extruded into a sheetapproximately 4 mm thick. A sheet is cut and the edges polished andLED's disposed at opposite edges of the volumetric scatteringlightguide. A white PET voided diffusely reflecting film is positionednear the opposite surface of the non-scattering region as the volumetricscattering film with an air gap between the reflecting film and thevolumetric scattering lightguide. Light from the LED's enters thevolumetric scattering lightguide and is coupled out due to thevolumetric scattering region in a uniform luminance pattern due to thelow refractive index coating reflecting high angled light from theLED's. The resulting light emitting device has a luminancemacro-uniformity and luminance micro-uniformity greater than 70%.

EQUIVALENTS

Those skilled in the art will recognize, or be able to ascertain usingno more than routine experimentation, numerous equivalents to thespecific procedures described herein. Such equivalents are considered tobe within the scope of the invention. Various substitutions,alterations, and modifications may be made to the invention withoutdeparting from the spirit and scope of the invention. Other aspects,advantages, and modifications are within the scope of the invention. Thecontents of all references, issued patents, and published patentapplications cited throughout this application are hereby incorporatedby reference. The appropriate components, processes, and methods ofthose patents, applications and other documents may be selected for theinvention and embodiments thereof. The contents of all references,including patents and patent applications, cited throughout thisapplication are hereby incorporated by reference in their entirety. Theappropriate components and methods of those references may be selectedfor the invention and embodiments thereof. Still further, the componentsand methods identified in the Background section are integral to thisdisclosure and can be used in conjunction with or substituted forcomponents and methods described elsewhere in the disclosure within thescope of the invention.

In describing embodiments of the invention, specific terminology is usedfor the sake of clarity. For purposes of description, each specific termis intended to at least include all technical and functional equivalentsthat operate in a similar manner to accomplish a similar purpose.Additionally, in some instances where a particular embodiment of theinvention includes a plurality of system elements or method steps, thoseelements or steps may be replaced with a single element or step;likewise, a single element or step may be replaced with a plurality ofelements or steps that serve the same purpose. Further, where parametersfor to various properties are specified herein for embodiments of theinvention, those parameters can be adjusted up or down by 1/20^(th),1/10^(th), ⅕^(th), ⅓^(rd), ½, etc, or by rounded-off approximationsthereof, within the scope of the invention unless otherwise specified.

1. A lightguide comprising: a) a first substantially non-scatteringregion comprising a first non-scattering light transmitting material; b)a first input surface of the first non-scattering region disposed toreceive light from a light source; c) a light extraction region disposedto direct a first portion of incident light to angles such that exitsthe lightguide; said light extraction region comprising a volumetricscattering region further comprising dispersed phase domains within alight transmitting matrix material; d) a low refractive index regiondisposed between and optically coupled to the first non-scatteringregion and the light extraction region, wherein the low refractive indexregion comprises a low refractive index material with a refractive indexless than the refractive index of the first non-scattering lighttransmitting material.
 2. The lightguide of claim 1 wherein the haze ofthe first non-scattering light transmitting region is less than 20%. 3.The lightguide of claim 1 wherein the light extraction region comprisessurface relief features.
 4. The lightguide of claim 1 wherein the lightextraction region comprises a volumetric scattering region furthercomprising dispersed phase domains within a light transmitting matrixmaterial.
 5. The lightguide of claim 4 wherein the volumetric scatteringregion scatters collimated laser light with a wavelength of 532nanometers incident normal to the surface of the volumetric scatteringregion into an angular intensity profile with an angular full-width athalf maximum intensity of greater than 2 degrees in at least one outputplane perpendicular to the surface of the volumetric scattering region.6. The lightguide of claim 4 wherein the refractive index of the lowrefractive index material is less than the refractive index of the lighttransmitting matrix material.
 7. The lightguide of claim 4 wherein theratio of the refractive index of the low refractive index material tothe first non-scattering light transmitting material is less than 0.98.8. The lightguide of claim 4 wherein the refractive index of the lowrefractive index material is at least 0.03 less than the refractiveindex of the first non-scattering light transmitting material.
 9. Alight emitting device comprising the lightguide of claim 1 and a firstlight source disposed to direct light into the first non-scatteringregion through the first input surface.
 10. A light fixture comprisingthe lightguide of claim 1 and a first light source disposed to directlight into the first non-scattering region through the first inputsurface.
 11. The lightguide of claim 1 wherein the light extractingregion does not directly receive light from a light source disposed atthe first input surface after it is transmitted into the firstnon-scattering region through the first input surface.
 12. Thelightguide of claim 1 wherein a plurality of dispersed phase domains arenon-spherical in shape.
 13. The lightguide of claim 1 wherein thelightguide is curved in at least one direction.
 14. The lightguide ofclaim 13 further comprising a first light emitting surface through whichlight exits the lightguide when the first input edge is illuminated by alight source, wherein the first light emitting surface is substantiallyshaped as an elliptic paraboloid.
 15. The lightguide of claim 13 furthercomprising a first light emitting surface through which light exits thelightguide when the first input edge is illuminated by a light source,wherein the first light emitting surface is substantially shaped as aparabolic cylinder.
 16. A light emitting device comprising thelightguide of claim 13, a first light source disposed to direct lightinto the first non-scattering region through the first input surface,and a light emitting device output surface, wherein the light emittingdevice output surface is substantially bulb-shaped.
 17. A light emittingdevice comprising the lightguide of claim 13, a first light sourcedisposed to direct light into the first non-scattering region throughthe first input surface, wherein the light emitting device is shapedsimilar to an Edison type incandescent light bulb, a parabolicaluminized reflector (PAR type) light bulb, an MR16 bulb, or a linearfluorescent bulb.
 18. The lightguide of claim 1 wherein the lightguideis tapered in at least one direction.
 19. The lightguide of claim 1further comprising a second non-scattering light transmitting regionoptically coupled to the light extracting region on the surface oppositethe low refractive index region.
 20. The lightguide of claim 1 whereinthe dimensions of the lightguide in first and second mutually orthogonaldirections are each greater than ten times the dimension in a thirddirection orthogonal to the first and second mutually orthogonaldirections.
 21. The lightguide of claim 20 wherein the smallest anglefrom the surface normal of the non-scattering region for light to reachthe volumetric light extracting region, θ_(s), is defined as$\theta_{s} = {\tan^{- 1}\left( \frac{D}{t} \right)}$ where D is thedistance between the first input surface and the light extracting regionin a direction orthogonal to the third direction and t is the thicknessof the first non-scattering region in the third direction, and thecritical angle from the surface normal of the non-scattering region forlight within the non-scattering region at the interface between thenon-scattering region and the low refractive index region, θ_(c), isdefined as$\theta_{c} = {\sin^{- 1}\left( \frac{n_{l}}{n_{ns}} \right)}$ wheren_(l) is the refractive index of the low refractive index material andthe n_(ns) is the refractive index of the non-scattering lighttransmitting material, and θ_(c)<θ_(s).
 22. The lightguide of claim 20wherein the distance, D_(min), is the shortest distance between thefirst input surface and the light extracting region in a directionorthogonal to the third direction and$D_{\min} > {t \times {\tan\left\lbrack {\sin^{- 1}\left( \frac{n_{l}}{n_{ns}} \right)} \right\rbrack}}$where t is the thickness of the first non-scattering region in the thirddirection, n_(l) is the refractive index of the low refractive indexmaterial and the n_(ns) is the refractive index of the non-scatteringlight transmitting material.
 23. The lightguide of claim 1 furthercomprising a first light emitting surface through which light exits thelightguide when the first input edge is illuminated by a light source,wherein the low refractive index region is disposed in a first spatiallyvarying pattern in a plane parallel to the first light emitting surface.24. The lightguide of claim 23 wherein the light transmitting matrixmaterial is directly optically coupled to the first non-scatteringregion in a region disposed in-between two low refractive index regionsin a first direction parallel to the first light emitting surface. 25.The lightguide of claim 23 further comprising air void regions disposedin a second spatially varying pattern in a plane parallel to the firstlight emitting surface.
 26. The lightguide of claim 25 wherein the lighttransmitting matrix material is directly optically coupled to the firstnon-scattering region in a third spatially varying pattern in a planeparallel to the first light emitting surface.
 27. A light emittingdevice comprising the lightguide of claim 1, a first light sourcedisposed to direct light into the first non-scattering region throughthe first input surface, a light emitting device output surface, whereinthe spatial luminance macro-uniformity of the light emitting deviceoutput surface is greater than 70%.
 28. The light emitting device ofclaim 27 wherein the light emitting device is a backlight forillumination of a display.
 29. A light emitting device comprising thelightguide of claim 1, a first light source disposed to direct lightinto the first non-scattering region through the first input surface, alight emitting device output surface, a square sub-region of the lightemitting device output surface nearest the first light source with equaldimensions of 20 times the thickness, wherein the spatial luminancemicro-uniformity in the square sub-region greater is than 70%.
 30. Alight emitting device comprising the lightguide of claim 1 and a firstlight source disposed to direct light into the first non-scatteringregion at the first input surface, wherein the light emitting device hasan optical efficiency greater than 60%.
 31. A light emitting devicecomprising the lightguide of claim 1, a first light source disposed todirect light into the first non-scattering region through the firstinput surface, a first light emitting device output surface, a secondlight emitting device output surface opposite the first light emittingsurface, wherein the percentage of light flux exiting the light emittingdevice from the first light emitting device output surface is greaterthan 50% and the percentage of light flux exiting the light emittingdevice from the second light emitting device output surface is less than50%.
 32. A light emitting device comprising a) the lightguide of claim1; b) a first light source disposed to direct light into the firstnon-scattering region through the first input surface; c) a second inputsurface of the first non-scattering region disposed opposite the firstinput surface; d) a second light source disposed to direct light intothe first non-scattering region through the second input surface; e) afirst light emitting device output surface; f) a first light emittingdevice optical axis for light exiting the first light emitting deviceoutput surface; g) a light redirecting optical element disposed toreceive light from the lightguide and direct a portion of the lighttoward the first light emitting device optical axis.